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| Authors: Sasa Kocic, Zoran Stojanovic
Traffic Accident Investigation Guidelines
With Reference to Desert Environments
1
Table of Contents Book review ............................................................................................................................................. 3
About the authors ................................................................................................................................... 4
Introduction............................................................................................................................................. 5
PREFACE .................................................................................................................................................. 7
Traffic accident terminology ............................................................................................................... 8
Factors of traffic safety ..................................................................................................................... 10
Human ........................................................................................................................................... 10
Vehicle ........................................................................................................................................... 12
Road ............................................................................................................................................... 15
Environment .................................................................................................................................. 18
Legal .............................................................................................................................................. 21
Securing the scene of the accident, ...................................................................................................... 23
Evidence identification and the ............................................................................................................. 23
On-scene measurement ........................................................................................................................ 23
Securing the scene of the accident ....................................................................................................... 24
Receiving the information ................................................................................................................. 24
Securing the scene and investigator safety ....................................................................................... 24
Placing traffic cones and traffic signs before the accident scene ................................................. 26
Using more than one vehicle ......................................................................................................... 30
Using another police officer, or a colleague to warn and regulate traffic at the accident scene . 31
Wearing a reflective west .............................................................................................................. 31
Knowledge of the investigation procedures ................................................................................. 31
Impact-crash phases: ......................................................................................................................... 32
Principles of the on-scene investigation ........................................................................................... 36
Main method of the on-scene investigation ..................................................................................... 36
Evidence identification ...................................................................................................................... 40
Traces that appear after the collision ........................................................................................... 41
Traces that appear at the point of collision .................................................................................. 45
Traces that appear before the point of collision ........................................................................... 52
Accident evidence found on the vehicles ......................................................................................... 67
Damage marks ............................................................................................................................... 68
Material marks .............................................................................................................................. 69
Wiping marks ................................................................................................................................. 69
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Casting marks ................................................................................................................................ 70
Abrasion, melting marks................................................................................................................ 70
Seatbelt examination .................................................................................................................... 71
On scene measurement ........................................................................................................................ 79
“Right angle coordinates” procedure ............................................................................................ 80
Triangle measuring procedure ...................................................................................................... 82
Measure curves ............................................................................................................................. 83
Measurement equipment ............................................................................................................. 86
Measuring damages on the vehicles ............................................................................................. 88
Photographing and filming the traffic accident evidence ..................................................................... 90
Photo cameras and lightning ............................................................................................................. 91
Digital photo camera ..................................................................................................................... 91
Camera lenses ............................................................................................................................... 92
System of Optical lenses................................................................................................................ 92
Aperture mechanism ..................................................................................................................... 93
Camera body ..................................................................................................................................... 94
Shutter mechanism ....................................................................................................................... 94
ISO Number ................................................................................................................................... 95
On scene photography ...................................................................................................................... 96
Investigation of the road design and construction elements ............................................................. 100
Road design elements ................................................................................................................. 101
Characteristics of rollovers on-scene investigation ........................................................................ 106
Characteristics of pedestrian and animal collision on-scene investigation ........................................ 113
Using software and additional resources ............................................................................................ 122
References ........................................................................................................................................... 127
3
Book review
The manual is clear and in accordance with the modern trends of accident investigation and
analysis. Illustrations, photos and examples from real life situations are used, as well as the
author’s experience from the Sultanate of Oman and Middle East.
The language used is plain and simple and the manual can also be used as a literary resource
for studies. High degree of expertise can be witnessed, confirmed by author’s experience
gained in Sultanate of Oman as well as international experience. The manual comprises a
positive trends and methods from USA, UK, Eastern Europe and Republic of Serbia, which is
mainly manifested in the practical examples and the references to the Road Safety Audit and
Road Safety Inspection elements.
Considering that the traffic safety system is based on the human, vehicle, road and
environment factors manual analyses each of these elements in depth as well as broader
analysis of the circumstances leading to the road traffic accident dependent on these
elements.
A high focus of the manual is towards the road and the environment, which is unfortunately
often neglected in the countries that do not have a system of traffic safety management.
The characteristics of the Sultanate of Oman as a country, primarily in terms of its climate,
high temperatures, and desert environment are put in focus as a part of the manual, in order to
show their influences on the traffic safety and the actual on-scene investigation.
Proper focus is placed also on the vehicle and human factors as causation factors of traffic
accidents. Elements of active and passive safety are also considered with special emphasis on
the In Vehicle Monitoring Systems and speed limiters.
The human factor got the most of the focus as the habits and potential mistakes in all phases
of planning, design and road maintenance up to the final mistakes during the driving, or in
other ways participating in traffic.
Based on the long term analysis of the authors work and experience, and the analysis of the
manual, I recommend this manual to the people engaged in the field of road safety, students
that are gaining the basic knowledge in the same field. I also recommend this manual to the
stake holders in the field of road safety as the help and guidance for overall understanding of
the road transport and road safety.
PhD. Demir Hadzich dipl. Eng.
Assistant minister for roads and traffic safety
Of Republic of Serbia
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About the authors
Sasa Kocic (English spelling: Sasha Kocitch) holds a University degree in traffic and transportation
and has worked for the past ten years in different fields of road safety. While working in the traffic
police in Republic of Serbia, he participated in the drafting of the new traffic safety law, and has also
participated in on-scene investigation and accident reconstructions in the city of Nish, Serbia. During
the recent five years Sasa has done more than 250 on-scene investigations and accident
reconstructions for Petroleum Development Oman and other companies in Oman. His experience
also covers the road and traffic design and therefore he was also able to combine this knowledge
and experience into the on-scene investigation and reconstruction. Currently his is working in
Petroleum Development Oman.
Zoran Stojanovic (English spelling: Zoran Stoyanovitch) holds a University degree in police sciences
and has worked for the last ten years in the on-scene investigation of traffic accidents either in the
traffic police in Serbia, or Road Safety Standards Team in Oman. He has participated in more than
100 on-scene investigations of the traffic accidents in Oman, and he is currently working as Road
Safety Standards Team Manager in Muscat, Oman.
Also, important contributor to the book is Mr. David Marsh who is currently working as Contract
Manager for the Road Safety Standards Team in Muscat, Oman. His experience of more than 15
years in the driver training has been very valuable in providing a wider insight of the driver training
and elements of the driver behavior identified as important for the on-scene accident investigator.
5
Introduction
The MAIN purpose of this manual is to present the principles and techniques of the on scene
investigation, based on the years of experience of on-scene investigations of traffic accidents and to
explain in deep the way on-scene investigation and later reporting is performed as a guideline for
the real-life on scene investigation.
The Manual is divided into four segments, each compatible with the course tailored for the on-scene
investigators and the steps that need to be taken during the on-scene investigation.
The segments are:
• Securing the scene of the accident, evidence identification and the on-scene measurement
• Photographing the evidences, scaled on-scene diagram production and evidence verification
• Vehicle examination, photogrammetric, advanced techniques of on-scene measurement and
evidence compatibility
• Usage of available software or data for the further in depth identification of the evidence
The FIRST thing is to define the road traffic accident, and here already you have a different
definitions of the traffic accidents (traffic crashes etc.).
The use of the accidents and crashes in the manual is deliberate because there is still a lack of
agreement in the traffic safety world of what is the proper name of this event (accident would mean
that it is the event under the influence of the higher force-like the will of god, while crash would
mean it is a consequence caused by the chain of events; but also considering that the accident is
something that had already happened and we want to learn from it and influence the future it
implies a bit of a higher force).
Anyway, this manual has no intention of going into the theory of etymology and therefore it will use
both the road traffic accident and traffic crash with the same meaning.
A definition of an accident could be:
“An accident is an unexpected or surprised incident which changes the situation of vehicles involved
as well as situations of passengers or pedestrians”. [66]
Or:
“An unwanted event where one or more moving vehicles participated and the harm to the person or
asset damage occurred” [1]
Accident investigation is a field of practice that requires specialized study, training and experience.
Accident investigation is the initial step towards the accident reconstruction and analysis.
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The on-scene investigation should provide enough evidence to answer the following questions [1]:
What?
Where?
When?
Who?
What with?
Whom with?
Why?
How?
To answer these questions the evidence taken from scene, persons and vehicles is very important.
This manual provides a brief description of on scene accident investigation methods which exist
today.
Some different software tools are described within this manual, but there is no recommendation
which one should be used. This is just the decision of the person or institution itself.
Sasa Kocic
7
PREFACE
The traffic accidents are random harmful events that involve different traffic participants and cause
fatalities, injuries or asset damage and are caused by one or combination of the following factors:
human, vehicle, road and environment.
But the traffic accidents are random and harmful events that can be reduced if we influence again
on one (but preferably on the whole) of the human, vehicle, road and environment factors.
Countries around the world invest different amounts of money or time into traffic safety with
different success in reducing the number or the severity of the accidents, and frequently these
investments are guided only by the public opinion and have no proper grounds in the actual accident
data.
He who defends everything defends nothing.
Frederick the Great (1712 - 1786)
The previous sentence describes the basic need of the accident data collection for the proper
management of funds, because without that data one can only guess where to focus and sometimes
this focus even brings more harm than benefit.
Traffic safety practitioners around the world sometimes do present solutions without the actual data
of the accidents (as their expert opinion), but this is true only to an extent that they do not have the
accidents data for the specific area that they are presenting the solution for and actually they are
usually comparing the actual location with some other similar location where they have gathered
the data from the traffic accidents.
Therefore proper data on accidents is needed to influence the traffic safety in a positive manner, not
to mention the proper data needed for the legal purposes of determining the liable party in the
accident.
To do this first we need to perform a proper accident investigation and data collection so that we
can reduce the ‘’random’’ element and identify in which fields we need to influence.
8
Traffic accident terminology
Area of impact: the place on the roadway or ground closest to the first contact between colliding
objects. [1]
Braking distance: the distance through which brakes are applied to slow a vehicle; the shortest
distance in which a particular vehicle can be stopped by braking from a specified speed on a
particular surface; the distance from brake application to collision. [1]
Cause(s): Actions, omissions, events or conditions, or a combination thereof, which led to the
accident or incident. [1]
Contact damage: damage to a vehicle resulting from direct pressure of some foreign object in a
collision or rollover. [1]
Crook: an abrupt change of direction of a tire mark due to collision forces. [1]
Debris: loose material strewn about the road as the result of a traffic collision; dirt, liquids, vehicle
parts, and other materials from the involved traffic units. [1]
Fatal accident: Injury accident in which at least one road user sustains a fatal injury. [1]
Fatality: Injury outcome resulting in death. [66]
Emergency Services: The services which can be accessed by dialing the emergency number,
including Police, Fire and Rescue, Ambulance service. [66]
Final position: the location of a vehicle or body when it comes to rest after a collision; final positions
may be controlled or uncontrolled. [66]
First contact: the initial touching of objects in a collision; the place on the road or ground where this
touching occurs. [1]
First harmful event: the first occurrence in a traffic collision that results in appreciable damage or
injury. [1]
Grade: the change in elevation in unit distance in a specified direction along the center line of a
roadway or the path of a vehicle; the difference in level of two points divided by the level distance
between the points. [43]
Injury accident: Road vehicle accident in which at least one road user sustains an injury. [1]
Induced damage: damage to a vehicle other than contact damage, often indicated by bending,
braking, and distortion. [1]
Maximum engagement: greatest penetration of one body, such as a vehicle, by another during
collision; moment of greatest force between objects in a collision. [66]
Pedestrian: it is a person traveling on foot, outside of the vehicle. [1]
9
Reference line: a line, often the edge of a roadway, from which measurements are made to locate
spots, especially spots along a roadway. [48]
Reference point: a point from which measurements are made to locate spots in an area; sometime
the intercept of two reference lines. [48]
Rollover: a situation where the vehicle rolls at least 90 degrees. The term rollover is also sometimes
used to describe a pitch over (vault). [49]
Raw data: Accident investigation data as it is collected and not yet processed or stored in a
database. [1]
Road user: Person on the road. [1]
Scrape: a broad area of a hard surface covered with many scratches or striations made by a sliding
metal part without great pressure. [1]
Scuff mark: a friction mark on a pavement made by a tire which is both rotating and slipping. [66]
Skid mark: a friction mark made on a pavement by a tire that is sliding without rotation. [66]
Skip skid: a braking skid mark interrupted at frequent regular intervals; the skid mark made by a
bouncing wheel on which brakes keep the wheel from turning. [66]
Traffic unit: an element of traffic; a person using a traffic way for travel or transportation; vehicle,
bicycle, pedestrian, animal etc. [1]
Vehicle occupant: Road user in or on a vehicle. [1]
10
Factors of traffic safety
There are different theories that describe the factors in traffic safety, each with its own explanation
and reference, for the purpose of this manual, five factors of traffic safety will be considered
(human, vehicle, road, environment and legal):
Human
Even if a vehicle with auto-pilot is produced and used widely, the human factor will remain the most
significant factor in traffic safety because there still will be pedestrians, bicycle riders, horse riders
etc. and the most precious element that the traffic safety strives to preserve will still be humans.
Human factors are incorporated in all of the elements of traffic safety influence:
Education- the most direct influence on human factor, considering that it provides guidance for the
people how to be a safe traffic participant.
Engineering –all of the road elements are designed with the influence of human factors, like brake
reaction time, sight distance, speed etc.
Enforcement – all the penalties are enforced on humans alone, and all of the enforcement
campaigns are focused on humans.
The human factor is vast and to describe it, it would take much more than this manual, as there are
already numerous books on human factors in traffic safety.
But in terms of accident investigation we need to focus on following elements of human factor, so
that we provide enough evidence for the further analysis and legal requirements in terms of
determining liability for the accident causation:
Gender: male or female
Age: the definitions on the child, adult, elderly varies and for the purpose of this manual any legal
definition is applicable
Nationality: needed as a reference for determining the training background, especially needed in
countries with large numbers of expatriates,
Health condition: in terms of general health,
Disability: in terms of physical disability,
Eye sight condition: in terms of the person’s legal requirement to wear glasses or lenses,
Influence of substances: in terms of alcohol, drugs or legally prescribed medicine that caused
impairment in terms of participating in traffic,
Height: required mostly for pedestrians,
Clothes color: required mostly for pedestrians,
11
Extent of Injury: in terms of severity of the injuries,
Location of injury: in terms of injury locations on the person’s body.
Way it participated in traffic: driver, passenger, pedestrian.
The elements mentioned above are found in different forms of accident reports which are filled in by
the on-scene investigators.
For the purpose of the manual, a simple form is developed as guidance for the development of the
complete Accident Investigation Formal Report.
Gender: Choose an item. Location of injuries for
pedestrian:
Age: Choose an item.
Nationality:
Health condition: Choose an item.
Disability: Choose an item.
Glasses or lenses: Choose an item.
Substances: Choose an item.
Height:
Color of clothes:
Extent of injury: Choose an item.
Status: Choose an item.
Location of injuries for drivers and passengers
12
Vehicle
Although mainly controlled by human, the vehicles have some of their own characteristics that need
to be identified in order to deliver a quality on scene investigation, and for the purpose of the
accurate and appropriate analysis of the traffic accidents.
Vehicles, most of the time influence the outcome of the traffic accident, and are seldom causation
factors for the accident.
On other hand vehicles and their parts provide a lot of evidence that helps in accident
reconstruction and determining the main cause of the accidents, considering that the vehicles leave
a lot of visible evidences on the ground and preserve a lot of evidences on themselves. [7]
This preservation of the evidences makes it possible to gather the evidences even if the scene of the
accident was disturbed by other people.
The state of the vehicle (in term of its roadworthiness) is also influencing the cause and the
consequences of the accidents and this is easily identifiable on the vehicle after the collision, or
based on the evidences from the vehicle.
Also the damages on the vehicle and certain vehicle parts can provide information on the driver’s
compliance with the law requirements (using a seatbelt, using lights etc.)
The evidences from the vehicle can be divided based on the part of the vehicle it was identified:
• Evidence made by the vehicle tyres
• Evidence made by or on the vehicle’s chassis
• Evidence on the vehicle’s windscreen
• Evidence on the vehicle lights and indicators
• Evidence on the vehicle’s steering wheel
• Evidence of the position of the vehicle’s commands (indicator leaver, gearbox leaver position
etc.)
• Evidence on the vehicle’s seats
• Evidence on the vehicle’s seat belts
• Evidence from the vehicle’s passenger and load compartment
13
The initial information that needs to be gathered about the vehicles is presented in the following
form:
Vehicle Type: Lights working:
Vehicle Make: Indicators working:
Vehicle Model: Seatbelts working:
Model Year: Brakes working:
Vehicle Reg. No: Rearview mirrors present:
Vehicle weight: Load weight:
Number of occupants: Tyre condition:
Sitting positions of the vehicle occupants and the damages on the vehicle (sedan):
Sitting positions of the vehicle occupants and the damages on the vehicle (4x4):
15
Later trough the manual it will be explained how to gather and compare the evidences from the
vehicles but these are the initial evidences that can be gathered on the spot or by testing the vehicle
in the workshops which can also be a part of the accident investigation although it does not take
part on the scene of the accident.
Road
The road itself can be considered as a sort of the drawing canvas that preserves the evidences of the
traffic accident participants prior to the accident during the accident and after the accident.
But the road itself also influences the causation and the process of the traffic accident.
The design and construction of roads should be such that all of the elements of traffic safety are
incorporated into the road design itself and later implemented through the road construction, but it
is usually not the case.
Due to the budget constraints the roads are designed and constructed as a result of the compromise
between the different requests in terms of traffic capacity, traffic safety, budgets and policy
requirements.
The road itself influences the causation of traffic accidents trough the different elements like:
Road layout- influences the driver’s perception of the level of safety and its driving behavior; also it
influences the driver’s choice of speed and the driver’s reaction time, [43]
Road profile- influences the driver’s sight distance and therefore its ability to realize the hazard in
time,
Road cross-section- influences the lateral forces that act on the vehicle in different occasions and
provides or denies easier maneuverability
Road surface- influences the deceleration rate of the vehicle, therefore influencing braking distance,
All of the three- the combination of the previously mentioned elements influences different
appearances of usually unexpected hazards like gaps in sight distance, sand accumulations, water
accumulations etc.
Therefore on-scene investigation needs to identify all of these characteristics and provide evidence
that will make it easy to decide on the engineering measures to be implemented to reduce the risk
of traffic accidents.
Therefore the identifying the road factor characteristics is very important, not only to determine the
causation and the liability for the accident, but also for reducing the gap between the traffic safety
and the other elements of road design and construction and therefore reducing the need for
compromise.
The influence of the road is sometimes disregarded in terms of the road safety and the people focus
on the actions of the participants in traffic and therefore a lot of accidents are contributed to the
driver’s failure to comply with the safe speed for the road conditions, and therefore the speed
16
makes such a significant factor in road accidents, thus a lot of countries keep on reducing the speed
limits.
This approach is however limited with the people needs for travelling and with the development the
distance the people need to travel increases therefore the lowering of the speed limits cannot go on
forever as the people would not want to spend most of their day in the vehicle travelling to or from
work.
The basic information that investigator should gather in regards to the road are:
Location of the accident on the road: (preferably GPS location)
Road type: Choose an item.
Road layout: Choose an item.
Road profile: Choose an item.
Road surface material: Choose an item.
Quality of road surface: Choose an item.
Any debris or obstacle on the road: Choose an item.
Road cross section
Fill Cut Cut and fill
Picture 1: Elements of the road cross section in rural areas (diagram from the
www.visualdictionaryonline.com)
17
Picture 2: Elements of the road cross section in urban areas (diagram from the
www.visualdictionaryonline.com)
Picture 3: Elements of the highway (diagram from the www.visualdictionaryonline.com)
18
Environment
Environment is a significant factor in road safety as it influences all previously mentioned factors in a
way that it is either impairing their characteristics (which is for accident investigator the most
important thing to determine) or providing a state that requires a different way of driving, vehicle
handling etc.
Most common environmental issue is the lighting, which can be depended on the time of the day, or
on the system of street illumination, we will also consider it as the first one because it is the one
influencing the driver primarily.
The lighting
In the element of lighting you also have the position of the sun, because if the driver was driving
towards the sun, considering that the sun can impair the driver’s possibility to realize the situation in
front and make it difficult to read the traffic signs, recognize the edge of the road, judge the distance
to the vehicle in front, or simply fail to notice the junction. The following pictures present the view
from the driver perspective onto the road ahead, with the sun shining directly to their eyes.
Photo 1: The influence of the sunlight on the driver’s view on the road, driving towards the sun
Photo 2: The influence of the sunset on the driver’s view on the road, driving towards the sunset
19
Also, driving at nigh represents a special case itself, as the driver is dependent on the lights of his
vehicle and the quality of the road markings to determine the position of his vehicle on the road.
Photo 3: The driver’s view of the road illuminated by the vehicle lights, with high quality road
markings
Photo 4: The driver’s view of the traffic sign blurred by the street lighting
20
Weather
Weather is also common element that needs to be determined when the on-scene investigation is
done, as the weather influences the driver, but it is a major influential factor for the vehicle and the
road. The rain is not common in Oman, or the Middle East as a whole, but it happens and when it
does influences, same as anywhere else in the world, the state of the road (wet asphalt roads,
especially if they have some sand on them have the same friction as if you are driving on ice), the
state of the vehicle (tyres have less friction, aquaplaning may appear), the driver (in the Middle East
when you get some relief from the heat it makes you feel comfortable and therefore may reduce
your awareness) and all of these combined creates a very dangerous driving environment which can
lead to accidents.
But also, bear in mind, Accident Investigator, YOU WILL BE DOING THE ACCIDENT INVESTIGATION IN
THESE CIRCUMSTANCES, AND THEREFORE YOU CAN ALSO BE IN A DANGER IF YOU DO NOT
CONSIDER THE WEATHER AND THE WAY IT INFLUENCES THE TRAFFIC SAFETY.
Safety first-do not became a part of the accident
More common weather influence in Oman is through the sand storms, which influence the driver
day and night and influence again all three previously mentioned factors (driver-reducing visibility;
road-creating debris or sand accumulations; vehicle-influencing the stability, friction etc.)
Photo 5: The view of the road in sandstorm
The basic information that investigator should gather in regards to the environment are:
Time when the accident happened:
Time when the accident investigation team
started the on-scene investigation:
Lighting conditions: Choose an item.
Weather: Choose an item.
Position of the sun in reference to the
driver’s view at the time of the on-scene
investigation:
Choose an item.
21
Legal
All of the elements in this sub-category are basically related to the previous four factors, and it is not
a common practice to put them into the separate category, but the authors of this manual
recognized the fact that the countries have different road and traffic related laws, rules and
guidelines and therefore it is advisable to consider this as a separate factor. The elements of this
factor are related to the driver, vehicle, road and environment and usually are collected during the
investigation as a part of the information that the investigator is gathering on the previous four
factors, only in this manual we separate them in order to show the importance of this factor to the
on-scene investigation and its influence on road safety.
One of the facts that contributed to the decision to present these elements as a separate factor is a
simple difference in the traffic related laws between the Sultanate of Oman and European Countries
i.e. the use of the seatbelts in rear seats is not mandatory in Sultanate of Oman, while it is
mandatory in most of the EU countries.
Also, the speed limits and posting of the speed limits is differently regulated and therefore have
legally different meaning in different countries.
The countries in the north are more concerned with rain and snow and therefore there are more
regulations in relation to the driving in adverse weather conditions. For instance the following sign is
very difficult to find in the Middle East, while it is common in the countries of northern hemisphere.
Picture 4: The “Ice” signs1
Also the following signs are common for the desert environment; while in other countries are
nonexistent or has a different symbol or meaning (i.e. camel is usually not a domestic animal in
Europe or USA):
Picture 5: The traffic signs common in the Middle East2
1 UK Traffic sign manual Chapter 4, combination of signs 554.2 and 554.3
2 Oman Highway Design Manual Section 19, Sign 121 and 150
22
In this manual the Legal factor is considered because the driver can only be held responsible for the
things that he was required to do, by the law, and he failed to do it, or for the things that he did but
was not allowed by the law.
In the field of traffic safety the principle of trust should be present and this principle is described in
the following sentence:
One should trust that if he is complying with the legal requirements, all other are also complying with
the legal requirements, but if he is not complying he should also assume that others will not be
complying with the legal requirements to the full extent3.
Basically, to explain this principle on an example, if the driver is aware that his brakes are not to the
full speck, or his tyres are old (in Sultanate of Oman the legal tyres must not be older than 4 years),
he should keep a longer distance regarding the vehicle in front of his vehicle, because in these cases
he will need a longer path to stop his vehicle if the vehicle in front is suddenly braking. On the other
hand, if the driver is fully compliant with the law, he can also expect that the posted speed limit is
the safe speed for travelling under the normal conditions, that the junction is clearly marked and
signed and that the person merging from the minor road will stop and give way to him.
The basic information that investigator should gather in regards to the legal requirements are:
Driving license number: Driving license
class:
Driving license restriction:
Vehicle registration: Vehicle class:
Vehicle loading:
BAC (blood alcohol concentration)
Speed limit:
Priority of the road:
Restrictions in relation to the road
condition:
Restrictions in relation to the weather:
Restrictions in relation to the road and
vehicle class:
(i.e. heavy vehicles are not allowed on the road
between 09:00 hrs and 13:00 hrs)
3 From the lectures on traffic safety in The faculty of traffic and transport engineering, University of Belgrade
23
Securing the scene of the accident,
Evidence identification and the
On-scene measurement
24
Securing the scene of the accident
Receiving the information
The information of the traffic crash can come in different ways, and it depends on the specific
organization of the country, institution or the company.
What it is important to get as the initial info is:
What happened (vehicle collision, collision with a pedestrian, collision with an animal, rollover etc.)?
Where did it happen (urban area, open road, gorge, bridge etc.)?
Is there anybody hurt?
Is the traffic disrupted?
Of course, this is only the initial info to help prepare for the on-scene investigation and bring a
proper kit, and also ask for help if you cannot handle the scene alone.
Securing the scene and investigator safety
Safety first-do not became a part of the accident
This is the sentence that should always be on the mind of the on-scene accident investigator.
There are only a few countries that allow a complete closure of the road for the sake of the on scene
investigation, and it is still a problem to provide enough safety to the investigators while performing
their duties on the scene of the accident.
The best way of securing the safety of the on-scene investigators at the moment is providing the
means for the investigators to be off road while performing the measurements.
Of course sometimes this is not possible to provide and therefore different techniques for providing
the safety of the investigators can be used, provided that there are enough resources.
One of the first resources available is the vehicle of the investigator.
The vehicles are usually distinctively marked and if positioned close to the road can give the
information to the other road users that some activities are performed on the road or close to the
road.
In this case the vehicle also serves as the safety buffer (crush cushion) in case some of the other
drivers does not notice the scene and does not manage to react in time.
25
Picture 6: The position of the accident investigator’s vehicle in relation to the scene serving as a
make shift crush cushion
Igniting the revolving lights and hazard warning lights is very important as they are a clear indication
that some emergency is going on.
Picture 7: The standard revolving light used on the police vehicles
Especially at night and during the reduced visibility conditions starting your revolving light means all
the difference for being safe at the scene of the accident.
Photo 6: The ignited revolving lights on a police vehicle at night
26
The other means of the investigator protection are also:
• Placing the traffic cones before the accident scene,
• Placing the appropriate traffic signs,
• Using more than one vehicle,
• Using a another police officer, or a colleague to warn and regulate traffic at the accident
scene
• Wearing the high visibility west,
• Knowledge of the investigation procedures.
First five elements are easily distinct, the sixth elements is a complex element of the application of
the investigators knowledge and the combination of different techniques, software and
measurement and evidence identification methods that, combined, provide enough validity of the
evidence but also provide a mean for the accident investigator to perform the measurements and
evidence gathering in a way that would provide him/her with enough safety not to become the part
of the accident scene or cause a hazard for other road users.
All of these methods and techniques will be presented trough the manual, and only to mention a
few, with a short description:
Photogrammetry (the pictures could be taken from the different positions, and combined with a
known measurements the measurements from the pictures can later be taken in the safety of your
office), with the digital cameras there is almost no limit to the number of the pictures that can be
taken on-scene and therefore take as many pictures as you can.
Parallel measurement (you do not have to walk on the skid mark or the broken glass in order to
measure its length, measure by walking off road or on the shoulder, calculate the unknown distance
from the known distance or measure (the traffic markings are usually standardized and provide a
known measure for the different types of road, therefore learn the standards of the road signs and
markings for the area you are in and apply that knowledge during the on scene measurement).
Placing traffic cones and traffic signs before the accident scene
This is intended to increase the buffer zone, to inform the oncoming drivers of the danger and
instruct them to preceded consciously trough the zone of the accident investigation.
The investigator should never forget that, except on motorways there is always traffic coming from
the opposite direction, therefore the drivers from the opposite direction should also be warned.
The scene should at least be secured with placed traffic cones and the portable signs.
This is the fastest way to inform other road users about the activities that are out of the ordinary on
the road and also quite frequently prevent other accidents from happening, considering that
sometimes accidents happen due to some damage on the road, spills etc. and by placing the traffic
cones and traffic signs the investigator is also helping in reducing the speed of the traffic on the road
section, increasing the road users awareness and providing guidance for negotiating the hazardous
road section.
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Picture 8: Increasing the buffer by placing the traffic cones before the accident scene
Photo 7: The actual placement of the traffic cones in buffer arrangement on the approach to the
accident scene
When the cones are placed as presented on the photo and the picture above there is a secure buffer
zone that is warning the drivers early enough, and also providing enough safety buffer for the
investigators in case something unwanted happens on the road.
The material carried usually depends on the vehicle which is used for the on-scene investigation.
European countries have the advantage that kombi vehicles can be used without a problem, as
presented in the following pictures, while the Middle East has a lot of graded roads and therefore
4x4 vehicles should be used. For urban environment in the Middle East kombi vehicle is also a good
option.
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Photo 8 and 9: The kombi vehicles with the cones and other material for on-scene investigation4
The good thing about graded roads is that the traffic is not dense and therefore the on-scene
investigators do not need to carry extra equipment for the securing of the on-scene investigators.
The basic equipment that this manual would recommend is presented on the following photos and
this equipment is easy to manage, store, maintain and carry around.
The equipment should be with retro-reflective capabilities in order to serve its purpose fully at
nighttime also.
Traffic cone (easy to use and does not require a lot of space, and can also be used as a tool for
marking the evidence)
Picture 9: The standard traffic cone
Photo 8: The portable traffic signs (preferably with the ACCIDENT AHEAD writing)
4 Photos taken from the web site of Serbian Ministry of Interior Affairs
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Photo 9: The flasher lights
Photo 10: Other portable traffic signs, flasher lights etc.5
Depending on the size of the vehicle and the loading capacity even a temporary barricades would be
recommended
Picture 10: The collapsible road barrier with flasher light
Mentioning all of this equipment is to again emphasize the importance of providing safety for the
on-scene investigators, because the accident has already happened, your life and your safety is
much more important than rushing in your job.
On motorways, expressways and generally roads with high speed limits, it is also a good idea if
investigator notifies and uses the help from the companies that are in charge of the road
maintenance, considering that their teams are usually well equipped for the performing work on
5 Picture of the on-scene investigation vehicle used by the Serbian traffic police
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these kinds of roads and their temporary traffic management kits are quite sufficient for the
temporary traffic management on the accident scene.
Photo 11: The road maintenance vehicle with built-in hazard warning and regulatory signs
Using more than one vehicle
This is very convenient tactic if it is possible to apply. It is especially useful in traffic accidents that
occur on the junctions, roundabouts, etc.
This tactic also usually considers complete road closure until the on-scene investigation is done,
therefore bear in mind that this is causing the disruption in traffic and in large cities it might cause a
lot of problems and traffic delays.
Therefore, complete closure of road is not recommended for a long time and the accident
investigator should also consider the severity of the accident, because, by using different equipment
and measurement and evidence gathering techniques you can also collect sufficient evidence
without creating a chaos in traffic.
Picture 11: Positioning vehicles for the T junction closure during the on-scene investigation
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Using another police officer, or a colleague to warn and regulate traffic at the accident
scene
Considering that when the traffic accident occurs a lot of people come to attend the scene and also
other police officers arrive in order to provide help, one of these persons can be used to regulate
traffic and provide a smooth enough traffic flow through the accident scene.
The proper way would be to use a traffic police officer, because they are trained in the field of
regulating traffic and they poses the knowledge and skills.
The optimal would be if only one police officer is needed to regulate traffic, because then the
motorbike patrol officer is an easy and appropriate solution.
Of course, sometimes one of the accident investigation team members needs to perform the traffic
regulation, and therefore it is recommended that all of the on scene investigators have the traffic
police officer training, and that a team is optimally formed from 3 members, so that the 2 members
can always attend the scene.
Wearing a reflective west
One of the major points in safety of the on-scene investigator is to make him visible and
recognizable from afar.
This is very important as the investigator is stepping on the road, to perform some of the elements
of the on scene investigation and his focus is on the work itself, therefore he must make sure that
other drivers see him.
Also, when the investigator is on the road second investigator should be helping him by scoping the
road from both sides and informing him of any oncoming vehicles.
Knowledge of the investigation procedures
Although the explanation is given before, this is just a reference to emphasize the importance of the
investigators knowledge, because the higher the knowledge the less time he needs to spend in
harm’s way.
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Impact-crash phases:
In order to perform a quality on-scene investigation, investigator should know the phases of the
crash, as each and every phase has its own set of evidences and the issues that need to be addressed
in order to perform quality on-scene investigation.
The first is the pre-crash phase which is the period in between the accident critical situation and the
first contact with the other vehicle. This phase is the accident initial phase. During this phase an
imminent accident can be indicated by critical driving maneuvers such as hard braking, skidding or
rapid steering inputs.
The second phase is the running-in period which includes the reaction of the driver from realizing
the situation until the first contact.
Third the phase is characterized through the run-out after an impact until the vehicle(s) stop(s) or
hits another vehicle.
Table 1: Crash phases6
Running-in
Behavior:
Impact
Behavior:
Run-out
Behavior:
o Realize situation o Running-in velocity o Run-out velocity
o Braking o Sliding o Etc.
o Sliding o Braking
o Steering o Steering
o Etc o Etc.
These crush phases usually go through the sequence of events that make a whole of any accident.
The sequence of events described here is the sequence of events that happens just before and
during the accident, until the vehicle, or vehicles come to their final rest position. All of these events
have their own characteristics and therefore have their own set of evidence that needs to be
gathered on the scene in order to describe the accident.
6 Adopted from the PENDANT Accident Reconstruction Guidelines
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Table 2: Common events in an accident
Point of possible perception - where a normally
attentive person in normal situation could have
perceived the hazardous situation. Always
comes at or before the point of perception.
Point of perception - where the (potentially)
hazardous situation is actually perceived by the
people involved.
Encroachment - is movement into the path
assigned to another traffic unit. Example:
crossing the centerline.
Point of no escape - that place and time beyond
which the accident cannot be prevented. The
position of this point in the chain of events can
vary considerably.
Start of evasive action - the first action taken by
any of the people involved in the accident able
to influence the movement of the vehicle or a
pedestrian to avoid a collision course or
otherwise avoid a hazard.
Line of sight
Line of sight
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First Harmful Event -the first occurrence in a
traffic accident that results in appreciable
damage or injury; the occurrence determining
the time and place of the accident; usually the
first contact in impact.
Initial contact -the first accidental touching of an
object collided with a traffic unit in motion.
Maximum engagement - the greatest collapse or
overlap in a collision: the deepest penetration of
the perimeter of the traffic unit.
Disengagement -separation of a traffic unit in
motion from an object with which it has collided.
Stopping and final position -where the vehicles
come to rest; the accident situation is stabilized
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The presented pictures show a typical sequence of events for the side collision at the junction.
Knowing the sequence helps the investigator identify the evidence, search for the typical evidence
for each of the sequence and identify the influence of the road, weather, geometry of the road and
the area layout.
Also, in single vehicle accidents the sequence is similar but there is no other participant to present
the hazard, rather the way the driver is driving, vehicle load or the road layout and condition, or the
combination of the above is the actual hazard.
All of the sequences in the rollover are presented in the following picture, but the events are in this
case basically matching in several instances:
Picture 12: The sequence of events in a rollover/tip over accident
In the previous picture, the point of maximum engagement and the point of initial impact are at the
same location, also the stopping and final positions are the same as the point of disengagement.
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Principles of the on-scene investigation
There are three basic principles of the on-scene investigation, therefore the principles of the
Investigation report:
• Principle of comprehensiveness (or the principle of the overall scope)
It requests that the on-scene investigation should cover all of the elements and the phases
of the crash, even with the reference to the previous events that did happen just moments
before the crash
• Principle of objectiveness
It requests that all of the evidence should be gathered objectively, and that subjective
evidences (such as witness statements, suppositions, assumptions etc. should be clearly
distinct and marked)
• Principle of compatibility
It requests that all of the evidences gather should be compatible and in conjunction with one
another [48]
Main method of the on-scene investigation
Back to front
This method is the most common method in the world for the on-scene investigation considering
that the on-scene investigation is based on the consequences of the crash and that the scene that
the investigator finds is the scene with the final rest positions and the post impact trajectories of the
crash participants.
Photos 11, 12, 13, 14: The accidents scenes and the evidence found at them
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And, of course, the worst case scenario (the scene has already been disturbed by the rescue teams,
unwanted visitors, police etc.)
Photo 15: The accident scene when the participants in the accident are removed from the scene
All of these cases provide a different challenge for the investigator, but when following the back-to-
front method of the investigation it possible to identify the proper evidence that is related to the
crash, its spatial relation and the connection and complement with other evidences.
This method is especially good when there are different evidences on the scene (usually there are
skid marks from other events, debris etc.) and the investigator needs to distinguish them from the
evidences that are related to the crash he is investigating.
Basically, this is a simplified process of elimination, considering that the evidences that do not lead
from the final rest positions are eliminated from the process of investigation.
There is sometimes a need to clearly distinguish the not related and related evidence but the back-
to-front method is convenient for initial distinguishing and later additional differences and facts
confirming that some evidence is not related to the accident can be acquired through measurement,
photography, comparison etc.
This method has its deficiencies, one of them being usually a difficulty to identify the final rest
position when the vehicles or other evidences have been tampered with by other people who were
on the scene (either a rescue service, people that were helping the participants in the accident etc.).
NOTE: Although the rescue service usually disturbs the evidences and it is not helping the
investigation, its agenda of helping the people injured in the crash is superseding the on-scene
investigation in any case. Bare that in mind when attending the scene of the crash together with the
rescue service.
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Evidence can be later correlated and interpolated from the evidences that are found people’s lives
and wellbeing is more important that determining what happened. However, this method should
preferably be used for the evidence identification, while the measurement, photographing etc. is
preferably done with a front-to-end method. The following example shows the proper way of
identifying the evidences that are related with the accident and their identification.
Table 3: Identification of the evidence in back-to-front method
Evidence Photo
The vehicle in final rest position
The scratch marks on the asphalt shoulder and
on the gravel shoulder leading to the final rest
position of the vehicle
Initial impact point on the asphalt from the
vehicle at the point where it first hit the
asphalt, while tipping over
The beginning of the skid mark of the vehicle’s
wheels
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At the same time, while identifying the evidences the investigator should place the evidence
identification elements (different stuff can be used for this; in the examples shown on the pictures
the simple plastic traffic cone is used) this way investigator has secured the scene of the crash and
identified the evidences and it is ready to perform the initial measurement of the scene and the
evidences identified.
One very important thing:
Do not tamper with the evidence, do not
move it, cover it, erase it or anything
else, just identify and capture it
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Evidence identification
Evidences of the collision are also called traces, and there is a several ways that the evidences are
classified [58]:
• Based on the size:
o Macro traces
o Micro traces
• Based on the phase of the accident in which they appeared
o Traces that generated before the accident
o Traces that generated during the accident
o Traces that generated after the accident
• Based on their location
o Traces on the road
o Traces on the off road surfaces
o Traces on the objects (buildings, fences, street furniture etc.)
o Traces on the vehicle
o Traces on the people or animals
• Based on the situation in which they appeared
o Typical
§ Real typical traces (usually appear in this type of accidents and belong to the
accident investigated)
§ False typical traces (usually appear in this type of accidents but do belong to
the accident investigated, maybe originated from some other accident that
happened on the same location in the similar way etc.)
o Non-existent (usually appear in this type of accidents but are missing in the accident
investigated)
o Atypical
Based on the previous classifications the traces that will be observed in this manual are:
• Traces that generated after the collision (after the initial impact and disengagement and up
to the stopping and final position)
o Traces on the road
o Traces on the off road surfaces and the objects
o Traces on the vehicle
o Traces on the people or animal
• Traces that generated during the collision (during the initial impact and disengagement)
o Traces on the road
o Traces on the off road surfaces and the objects
o Traces on the vehicle
o Traces on the people or animal
• Traces that generated before the collision (from the point of perception to the initial impact)
o Traces on the road
o Traces on the off road surfaces
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Traces that appear after the collision
Skid marks from the point of impact to the point of final rest position
Photo 15: The skid marks from the point of impact to the final rest position generated in a crush test
Photo 16: The skid marks from the point of impact to the final rest position identified in the actual
accident
The previous pictures show the traces on the road that lead to the final rest position of the vehicles.
If the vehicle was not moved from the scene these traces are easily detectable and identifiable.
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When it comes to the skid marks, if they appeared between the point of disengagement and the
final rest position they have to finish beneath the wheels of the vehicle, if the vehicle did not rollover
or tip over after the collision.
These traces are also very important in determining the initial point of contact (basically the point of
collision).
The investigator should be aware that in some cases these marks do not start at the point where the
vehicle initially impacted as the vehicle might have been in the air, or the marks are ‘’overwritten’’
by some other marks (like scratch marks) which are more distinctive than the skid marks.
Debris
Due to the impact with other vehicle, pedestrian, object etc. the parts of the vehicle get damaged
and detached from the vehicle.
After the impact they either travel for a certain distance and then fall on the ground, or are carried
by the vehicle and fall on the ground after the vehicle has stopped.
In any case these traces should be identified and related to the vehicle from which it came from. As
it is also possible that some of the traces are actually from some other vehicle that had an accident
on the same place and were not removed after the scene was cleaned.
This debris usually travels under the influence of inertia; therefore it shows the direction the vehicle
was travelling.
Following pictures show the effects of inertia and the way the debris (crushed parts) are travelling.
Photo 17: The debris and its travel path generated at the point of impact at maximum engagement
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Photo 18: Debris and its travel path generated at the point of impact at the time of disengagement
When it comes to rollovers the debris shows the path the vehicle traveled during the rollover
motion, and the places it hit during its rollover motion.
Photo 19: Debris and its travel path generated during a rollover
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Other traces of debris would be the things that pedestrian has carried on him when he was struck by
a vehicle and these things should also be identified.
Photos 20 and 21: Debris in a form of a belongings carried by a pedestrian generated in a pedestrian
collision
Traces of blood and other biological traces
These traces can be identified on the ground usually in accidents with the pedestrians, when the
occupants are thrown out of the vehicle or in collisions with the animals.
Usually these are blood stains that are located at the points where the body finally rested or the
point where a significant impact to the ground appeared and the injury was such that the blood
dropped on the ground.
Photos 22 and 23: Blood stains and biological traces on the windscreen and the road
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Traces that appear at the point of collision
Scratch marks
The most common traces that appear at the point of collision in vehicular accidents are the scratch
marks.
They appear as a result of the interaction between the vehicles where the forces that influence the
vehicles during the collision make the front parts of the vehicle go down to the ground and scratch
the surface with its metal parts as a result.
Photo 24: Vehicle movement at the point of impact (extracted from Toyota Yaris crush test)
These scratch marks are quite distinctive on the asphalt and provide a quite accurate identification
of the point of collision. The scratch mark from collision is presented on the photo bellow:
Photo 25: Scratch mark on the asphalt indicating the point of collision
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Scratch marks can show the initial point where the vehicle, starting to rollover, initially impacted the
ground and also the direction the vehicle slid after it first impacted the ground. The distinctive
scratch mark is shown on the following photo:
Photo 26: Scratch marks on the asphalt indicating the point of initial impact to the ground and
direction of travel
Scratch marks can also appear if the wheel suffers punctured tyre and the tyre disassembles (gets
completely thorn off) and the wheels is scratching the asphalt with the metal of the rim. Also, in
some cases (if the wheel was not appropriately bolted) the whole wheels assembly comes off and
the metal of the wheel drum scratches the asphalt.
In order to confirm that these scratch marks belong to this vehicle the investigator should compare
the damages on the vehicle and match them with the scratch marks on the road.
The following photos show the scratch mark made by the wheel drum, in case when the wheel came
off the axle during driving and caused the driver to lose control of the vehicle.
Photo 26: Scratch mark on the asphalt created by the wheel drum leading to the final rest position
47
On the previous photo the scratch mark is identified on the asphalt surface leading to the final rest
position of the vehicle.
The photos bellow show the damages and remains of asphalt pieces on the wheel drums confirming
that the scratch mark is caused by the vehicle wheel drum and that the wheel came off.
Photo 27: Matching marks the wheel drum that created a scratch mark on the asphalt (example of
the principle of compatibility)
Also scratch marks can appear before the rollover if the vehicle’s tyre comes off the wheel rim due
to the pressure on the side wall of the tyre.
Photo 28: The creation of the scratch marks at the beginning of a rollover whit a tyre disconnecting
from the rim7
7 Picture extracted from the NHTSA rollover crush test
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Transformation or discontinuation of the braking marks
Photo 29: The transformation of the skid marks at the point of collision
The marks shown on the previous photo usually appear at the point of collision when the vehicle
collides with another vehicle and stops moving forward and due to the forces of the collision start
rotating or moving sideways.
The increase in intensity and sometimes the width of the skid mark at this point is due to the force of
the impact acting on the wheels and pushing them down towards the ground, when the tyre is also
pushed down and the contact surface between the tyre and the ground increases:
Photo 29: The deformation of tyre at the point of impact under the influence of the impact forces
This kind of discontinuation and transformation of the skid marks is often accompanied with the
scratch marks on the asphalt surface:
Photos 30 and 31: The combination of the transformed skid mark and the scratch marks at the point
of collision
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The following photo shows the position of the vehicle and the disturbance in the braking marks at
the point of collision, and as it can be seen the rear wheels braking marks can also leave
discontinued and transformed braking marks that indicate the position of the rear wheels in the
point of collision:
Photo 32: The transformed skid mark of the rear wheels of the bus indicating the position of the rear
wheels at the time of impact
This disturbance can also appear in the side collisions, as the vehicle is influenced by the side impact
from another vehicle and therefore the vehicle moves from the straight movement and the braking
marks discontinue their straight course on this point.
The braking marks can completely disappear, if the vehicle was lifted in the air as a result of collision,
or transform into skid marks if the vehicle trajectory was moved, but the wheels still remained on
the ground.
Picture 13: The transformation of the braking marks into a side skid marks due to lateral impact
In the case of collision with a pedestrian or an animal investigator can expect a short increase in
intensity on the braking marks in the point off collision, as the weight of the pedestrian’s or animals
body increases the weight that is acting on the wheels.
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If the pedestrian or animal was impacted with one side of the vehicle, the intensity will be larger on
that side and it can happen that the trajectory of the vehicle’s braking marks changes towards the
side of the impact.
In cases of pedestrian and animal impact investigator can also expect to find the marks of the
pedestrian shoes or the animal’s hooves, like the ones shown on the photo bellow:
Photo 33: Scratch marks from camel’s hooves at the point of impact
Photo 34: The increase in intensity and the swerving of the vehicle braking marks in the point of
collision with a camel
Point where the intensity of the
braking marks appear and the
braking marks swerve to the right,
indicating the point of collision with
the camel and the fact that the
camel was hit by the front right part
of the vehicle
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Vehicle fluid marks
At the point of collision, as a result of the damage to the vehicle investigator can also find the tracers
of coolant spill, oil spill or even a fuel spill.
Photos 35 and 36: Lubricant and coolant water spill at the point of collision
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Traces that appear before the point of collision
Driving marks
Driving marks are vehicle tyre imprints in soft surface. Driving marks are easily identified in the sand
and gravel; sometimes it is also possible to find them on wet asphalt, if the investigator comes in
time so that the asphalt surface is not yet dried, or there is an oil spillage on the road and the vehicle
drove through it.
Photos 37 and 38: Driving marks in a sand and after driving trough the water pond
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Of course it would be perfect if the driving marks are imprinted on the sand like presented on the
previous picture of the tyre marks on the sand, but usually that is not the case, and most likely the
case will be more similar to the following picture:
Photo 39: The actual situation with driving marks on a gravel road
Then investigator can use one or both of the principles of the accident investigation
(comprehensiveness and compatibility).
Principle of comprehensiveness requires to investigate the scene as a whole, therefore the driving
marks that end at the beginning of the skid marks or at the point the vehicle went off road
(identified by some damage or debris) are the driving marks that belong to the vehicle.
Principle of compatibility requires that the thread of the tyre is the same as the imprint on the road.
Therefore the tyre marks on the presented picture belong to the ATV vehicle (quad)
Photo 40: Applying the principle of compatibility to compare the tyre and the marks and determine
the actual source of the tyre marks
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Skid marks
Skid marks are the imprints of the tyre sliding on the road surface. Sometimes they are equalized
with the braking marks but for the purpose of this manual, the skid marks will be considered only as
the marks made by a laterally sliding tyre.
These marks are characteristic for the rollover accidents, as the vehicle goes out of control and starts
sliding towards one of its sides.
The skid marks appear on the asphalt surface as the result of the tyre sliding across the surface and
thus creating enough heat to melt the thread of the tyre and also influence the bitumen in the
asphalt to heat and rise to the top of the asphalt and the melted pieces are imprinted onto the road
surface.
Research shows that the tyre imprints usually appear approximately 2 meters from the point the
vehicle actually starts to skid.
This is the case only on asphalt surfaces, on concrete surfaces the skid marks appear as a result of
the tyre pieces being scratched away from the tyre and are not in direct relation to the temperature
created by the friction between the road surface and the tyre, the tyre parts are presented in the
following photo:
Picture 14: Parts of the tyre
On gravel and sand the tyre pieces will be more difficult to find and the usual skid marks that appear
in these cases are the skid marks made by the tyre pushing the sand or gravel and smooth the
surface bellow as it skids across it.
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The following photos show the characteristic skid marks.
Photo 41: The skid marks made by the vehicle skidding sideways, with visible striations
The previous photo shows the characteristic skid marks that appear when the tyres of the wheels
are sliding across the asphalt surface and the wheels are still spinning, therefore the skid marks
create striations which are easily identifiable on the skid marks.
Photos 42 and 43: Enlarged striations of the vehicle tyres skidding sideways prior to the vehicle
rollover
These striations also indicate the direction of travel of the wheel (vehicle) at the time the striation
marks are made. And this is quite helpful if the vehicle was removed from the scene and the skid
marks are not bended enough to show the direction of travel of the vehicle.
56
Following photos are from a real life rollover caught on camera, and they show the actual skid
marks and its relation to the vehicle movement in an anticlockwise skid before the rollover, where
the increase in the intensity of the skid marks is evident from the start of the skid mark to its end:
Photos 44 and 45: The start of the skid mark creation and the end of the skid marks at the point
where the vehicle becomes airborne
The skid marks on the gravel surface are not that easily detectable and the best practice would be to
start from the final rest position of the vehicle and go backwards.
Photos 46 and 47: The skid marks on the gravel or sand surfaces
Photo on the left also indicates the striation marks of the tyre on the surface, but it takes much more
effort to identify striations on the gravel roads and therefore taking close-up photographs of the skid
marks is essential in on-scene investigation.
There are also skid marks that appear when an articulated vehicle (prime mover with trailer) is jack
knifing. They can appear as a result of the vehicle jack-knifing due to the driver over steering or due
to the driver both over steering and braking.
In the case of the driver over steering only skid marks appear, while in the case of the driver both
over steering and breaking the braking marks transform into the skid marks.
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Photos 48, 49 and 50: Characteristic skid marks for jack-knife accident
Previous photos show the vehicle in final rest position of the vehicle that has jack-knifed and the skid
marks leading to the vehicle, with the characteristic crossing of the skid marks made by the tyres of
the front wheels.
Picture 15: The top view of the skid marks characteristic for the jack-knife accident
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Braking marks
Braking marks have the similar characteristics as the skid marks. They also appear on the asphalt as
the result of the tyre sliding across the surface and thus creating enough heat to melt the thread of
the tyre and the melted pieces are imprinted onto the road surface and also influence the bitumen
in the asphalt to heat and rise to the top of the asphalt.
Research shows that the tyre imprints usually appear approximately 2 meters from the point the
vehicle actually starts to skid. But in case of the braking the wheel is stopped from spinning and
therefore chevron like marks will not appear (striation marks).
Also on concrete surfaces the braking marks appear as a result of the tyre pieces being scratched
away from the tyre and are not in direct relation to the temperature created by the friction between
the road surface and the tyre.
On gravel and sand the tyre pieces will be more difficult to find and the usual braking marks that
appear in these cases are the braking marks made by the tyre pushing the sand or gravel and smooth
the surface bellow as it skids across it.
The following photos are taken by the thermal camera and they show the heat regions on the wheel
disks and brakes and also on the surface of the tyre and in between the tyre and the asphalt:
Photos 51 and 52: Thermal camera images of the creation of braking marks (extracted from the
presentation video of InfraTec)
The photos show that the wheel braking discs are heated to almost the same temperature during
braking, while the heat on the tyre thread area is rapidly increasing, and the tyre pieces are getting
melted away from the tyre thread area and falling down on the ground.
The importance of the braking marks is quite higher than other evidences that investigator can find
on the road due to the high number of information that can be gathered from the braking marks
itself, just by analyzing their layout, intensity and length.
The main importance of braking marks is that they show the exact driver’s reaction and remove the
speculation.
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Basically, if there are no braking marks on the road the evidence of the driver’s reaction is missing as
there are many ways the driver can react on a perceived hazard.
Some drivers decide to steer instead of braking, some increase the speed of the vehicle in order to
move away from the hazard as soon as possible, and some fail to react at all.
When there are braking marks we have hard evidence where the driver realize the danger and
decided to engage the evasive action, and what this evasive action was.
In order to understand the braking marks we need to understand the principle of braking.
The braking system of any vehicle is engaged by applying a force on the brake command (which can
be a pedal or a handbrake leaver).
Picture 16: Elements of the braking pedal
The command is later transferred trough the vehicles braking system onto the brake cylinders and
onto the brake discs and/or the brake pedals.
Picture 16: Elements of the braking system
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Master Cylinder
The master cylinder acts as a holding tank for brake fluid until it is needed. When the brake pedal is
depressed, the master cylinder forces fluid to each of the vehicle's wheels. [54]
Picture 16: Elements of the master cylinder
Combination Valve
A vehicle's wheel can lock up if the front and rear brake systems are not working together properly.
Comprised of a metering valve, proportioning valve, and brake warning light, and the combination
valve helps regulate the amount of pressure on each set of wheels -- making sure both front and rear
brakes are applied at the same time. [54]
Picture 17: Elements of the combination valve
Wheel Cylinder
The wheel cylinder is a critical element in the drum brake assembly. It contains fluid-activated
pistons that push the shoes against the drums to slow the wheels. [54]
Photo 53: Wheel cylinder
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Disc Brake Assembly
Because a disc brake assembly can absorb more heat than a drum brake assembly, most cars use
disc brakes for their front brake systems. When the brake pedal is pushed, brake fluid from the
master cylinder compresses the brake pads against the rotors attached to the vehicle's front wheels.
The friction between the stationary pads and the revolving rotors causes the rotors and wheel to
slow and stop. [30]
Picture 18: Elements of the disc brake assembly
Drum Brake Assembly
A drum brake assembly uses brake shoes to act against the walls of the wheel assembly to create
friction and force the wheel to stop rotating. Fluid pressure from the master cylinder causes the
wheel cylinder to push the brake shoes against the brake drums which are attached to the vehicle's
rear wheels. The friction between the stationary shoes and the revolving drums causes the drums to
slow and stop the rear wheels. [30]
Picture 18: Elements of the drum brake assembly
Heavy vehicles and articulated vehicles have a bit different layout of the braking system but the
principles previously presented apply also to these vehicles.
When the force of the brakes stops the wheel from spinning it locks into a standstill position and the
friction between the tyre and the asphalt increases.
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Picture 19: Forces created by the effect of braking
The vehicle starts to slow down and the tyres start leaving visible braking marks.
These braking marks continue until the vehicle collides into some other vehicle, object, human or
animal.
The braking marks then show different elements of the accident, which can provide evidence for the
state of the tyres, air pressure inside the tyres, initial point of impact etc.
Braking marks shown in the following photo are the braking marks of the properly inflated, fully
locked wheels positioned straight in relation to the vehicle’s movement.
Photo 54: Braking marks on asphalt
Braking marks shown on the following photos show that the tyres of this vehicle were underinflated
(as the sides of the braking marks are distinctive from the center of the braking marks):
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Photos: 55, 56 and 57: Braking marks on the asphalt indicating that the tyre was underinflated
The under inflated tyres leave more distinctive marks on the edges of the tyre as it brakes on the
asphalt.
Investigator should also note that these kind of traces are easy to distinct on the asphalt while on
the gravel and sand surfaces are more difficult as the traces of the tyre are not easily detectable and
instead the traces of the wheel pushing the soil is the trace that is detected.
Photos: 58 and 59: Braking marks on the gravel surface
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Braking marks can also show the way the driver reacted.
Photos 60 and 61: Showing that the driver first reacted by steering to the right and then applied
brakes
The previous statement is confirmed by the fact that the braking marks are veering to the right and
that the near side braking marks have higher intensity than the off side braking marks.
The off side braking marks have lower intensity as the driver, by steering to the right influenced the
vehicle movement and also the location of its center of gravity and the vehicle leaned to the right,
therefore reducing the weight that was acting on the off side wheels of the vehicle. The reduction of
the weight resulted in the less friction on the wheels and therefore the temperature created on
these wheels is lower, therefore producing lower intensity of the skid mark. These skids marks later
usually increase their intensity and become the same as the skid marks of the wheels on the
opposite side. The skid marks on the right are with higher intensity again due to the weight shift and
the friction force is increased on the wheels resulting in higher temperature.
In some cases, especially when the driver reacts harshly and at higher speeds the wheels on the
opposite side from the side the vehicle is turning towards can even detach from the asphalt and for
some distance do not even leave the visible skid marks. Later the skid marks appear when the
vehicle regains its balance but the difference in the length of the skid marks can be quite significant.
Photo 62: Skid marks that appeared when the driver decided to overtake the vehicle in front of his
vehicle at higher speed, and after realizing that it will not be possible harshly steered to the right and
applied brakes.
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In the cases when the difference in skid marks appear the investigator should always check the
braking system of the vehicle, as these kind of differences can also appear due to the faulty braking
system, not only due to the weight shift.
Skip skid braking marks
Photo 63 and 64: Skip skid braking marks from the unloaded trailer
These braking marks appear usually when the unloaded or lightly loaded trailer or is braking on the
downhill or on an asphalt surface which is not smooth enough (wave like).
Gap skid braking marks
These braking marks appear when the driver applies the brakes, releases them and then applies
them again. The gap in the skids is larger than the gap that can be seen in the skip skid braking marks
or ABS braking marks.
This kind of gap is usually the result of the driver’s inability to recognize the hazard to a full extent.
Therefore the first reaction is instinctive reaction towards reducing the speed, and later reaction is
the actual reaction when the driver fully realizes the hazard and makes a decision on the avoiding
maneuver (braking). Sometimes the driver also steers together with applying brakes.
ABS skid braking marks
Antilock brakes work on the following system: wheel speed sensors determining when a wheel is
locked or on the verge of locking and momentarily release brake pressure to prevent the wheel from
locking. Therefore this effect can be seen in the dotted skid marks. The tire marks appear where the
brakes lock; the clear spaces are where they’re released. The following photo presents the braking
mark produced by the ABS braking system.
66
Photo 65: ABS braking marks
Also, at low speeds the heat produced by the ABS is not enough to leave the visible traces of the
braking marks and therefore sometimes investigator can wrongly assume that the driver did not
even apply brakes.
On all paved surfaces, ABS braking marks are lighter and harder to see than a skid mark, as
presented in the following photo (ref. http://www.tarorigin.com/art/absscuff/index.html).
Photo 66: Difference between the skid marks and ABS braking marks
Following elements investigator should bear in mind when investigating accidents where some of
the vehicles has ABS:
• Dry surface ABS braking marks are most easily viewed in the direction of vehicle approach,
at some distance from their beginning, and at a small angle.
• ABS braking marks are short-lived evidence.
• Steering inputs can be apparent within the ABS braking mark.
• On wet surfaces it is very difficult to find traces of the ABS braking marks.
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Accident evidence found on the vehicles
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Damage marks
Damage marks result from the collision of a vehicle with at least one collision opponent. This could
be another vehicle, person, obstacle, building, etc. The existing damage traces permit conclusions on
driving directions and collision positions of the collision opponents to each other.
Photos 67, 68, 69 and 70: The damages of the vehicles resulting from the collision:
Based on these damages it is easy to determine the vehicle positions in the point of collision, as the
damages should correspond to one another.
Picture 17: The re-enactment of the vehicle collision positions at the point of impact
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Material marks
Material marks are traces that can be found on the accident scene whereby the material is still
clearly recognizable in its form/structure. They can provide the information on the impact positions
of the vehicles, help in identifying the position of the vehicle occupants inside the vehicle etc.
Also they can be used to identify the vehicle if it was for some reason removed from the scene of the
accident.
Photos 71 and 72: The plastic fender with a license plate and the sign of the manufacturer of the
vehicle that got detached from the vehicle during impact
Based on the previous photos, accident investigator can easily determine the make and the owner of
the vehicle that was removed from the accident scene.
Wiping marks
Wiping marks develop if the vehicle touches another vehicle, a person, some object or an animal.
Dust and dirt particle are wiped by the surface of the vehicle or the floor pan. Wiping traces can be
assigned due to their characteristic form and the determined height of the contact point between
the collision opponents can be measured. The photos bellow show the wiping marks made by the
different objects.
Photo 73: The wiping mark from pedestrian standing; Photo 74 Wiping mark made by the pedestrian
hand while being run-over by a tyre
The wiping marks are useful for determining the actual point on the vehicle which collided with a
pedestrian, animal or object because it later shows the position of the pedestrian, animal or object
at the point of impact. The pedestrian and animal are usually thrown from the point of impact and
their positions at the point of impact are crucial to determine.
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Casting marks
Casting marks result from transmission of a specific surface sample on the vehicle or on the tyres.
The sample is basically a negative of the different surfaces that come in contact. The picture on the
left side shows marks from an object on the tyre and on the right picture the object which made this
marks is shown. This is clear evidence that the vehicle drove over the object with its wheel.[66]
Photos 75 and 76: Casting marks and the source of the casting marks
Abrasion, melting marks
Abrasion marks develop with contacts of two vehicles or a vehicle with an object whereby abrasion
marks from one vehicle/object are transferred to another vehicle/object and vice versa. Most
common abrasion marks at the vehicle are colors, transferred rubber and plastics blood, hair and
textile fibers. These traces give information of the direction of motion, the course of motion and the
position of the vehicles/persons involved in an accident at the time of the collision. [66]
Photos 77 and 78: Abrasion marks of color from one vehicle to another
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Seatbelt examination
Using seatbelts is mandatory all over the world. It only depends which occupants are obligated to
use them, as sometimes only the occupants in the front of the vehicle must use the seatbelts. And it
is important for the investigator to determine if all occupants were using the seatbelts, or at least
the occupants that were required by the law to use the seatbelts did comply with the law.
Photos 79 and 80: The seatbelt was not usable-damaged
Unfortunately, on-scene evidence is not always that obvious, therefore the investigator needs to
identify the evidence that will confirm seatbelt use or provide proof of not using a seat belt.
Investigator should examine and photograph the following elements of the seat belt system in order
to provide the full evidence of the seatbelt use.
Picture 18: Elements of the seatbelt system
• Retractor
Photo 81: The retractor is found jammed, and the seatbelt is extended (this proves that the
person was using a seatbelt)
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Investigator should be careful not to mix this evidence with the similar position of the seat
belt when a vehicle occupant buckles its seatbelt behind its back.
Photo 82: The retractor is not jammed, but only the seatbelt is extended
Also, retractor frame can be damaged when the inertia force of the occupant body weight
acts as a seatbelt load:
Photo 83: Damages on the retractor frame
• D-ring
While investigating the seatbelts, the investigator should investigate the presence of
striations on the plastic of the D-ring, as they are created by the sudden and intensive
movement of the seatbelt webbing over the D-ring plastic, as shown on the following
photos:
Photos 84 and 85: Striations on the D-ring created by the sudden movement of seatbelt
Photo 86: The D-ring damaged as the result of the force of the body movement and seatbelt
retraction
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• Webbing (the belt itself)
Previously mentioned striations are often accompanied by the compatible imprints on the
seatbelt webbing, as presented in the following photo:
Photo 87: The striations on the seatbelt webbing
Also from the D-ring (and Latch plate-buckle), plastic transfer (as plastic melts due to the
heat induced by the movement of the seatbelt) can be recorded on the seatbelt webbing.
Photo 88: The plastic transfer from the D-ring onto seatbelt webbing
The webbing can also get the clothing transfer (transfer of color or fabric from the
occupant’s clothes):
Photo 89: The clothing transfer onto a seatbelt webbing
Previous evidence should not be misinterpreted for the dirt that can also be found on the
seatbelts.
• Buckle and latch plate
The latch plate (plastic around the buckle) can be found damaged due to the force of the
body and the seatbelt retraction, as shown on the following photo.
Photo 90: damaged latch plate
Also, seatbelt buckle stalk can be deformed due to the influence of the force (and it will
always be moved towards the seat of the occupant using the seatbelt), as shown in the
following photo:
Photo 91: The deformation of the seatbelt buckle stalk from the force of a seatbelt
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In some rear cases of the rollover the occupants can be thrown out of the vehicle even if they were
using the seatbelt, but in most of the accidents this is not the case.
In order to provide a solid evidence for the people not using the seatbelt investigator should again
apply the principle of compatibility and comprehensiveness (or the principle of the overall scope),
and provide the compatible evidence of the damages on the steering wheel, as shown on the
following photos:
Photos 92 and 93: The damaged steering wheel from the driver’s body (driver not using seatbelt)
The steering wheel is damaged by the driver’s body moving unrestrained and therefore the evidence
is confirming that the driver was not using the seat belt.
Also, the damages on the windscreen, originating from inside, and the traces of blood, skin and hair
are also confirming the movement of the occupant’s body, which would not happen if the occupant
was using the seatbelt, and therefore confirming that the person was not using the seatbelt:
Photos 94 and 95: The damaged windscreen and biological traces on the windscreen remained after
the impact of the vehicle occupant (occupant not using seatbelt)
Biological traces
Biological traces in this sense (traces at/in vehicles or at persons) are separated, withdrawn, abraded
or separated materials or parts of an organism (humans, animal or plant). In the context of an
accident these are blood, hair, fabrics and secretions, brain mass, body and bone parts, skin parts.
Photos 96 and 97: The biological traces on the inside of the windscreen
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Airbag control unit
The airbag system consists of modules and a control unit. Modules are in steering wheel, doors, dash
board. Furthermore there is a microcontroller which consists of CPU, analogue/digital transducer,
storage unit and communication interface. Storage unit consists of a read memory (ROM), read and
write memory (RAM) and an electric programmable storage unit (EEPROM).
Data which are stored in airbag control units (EEPROM):
• System and failure status before and during collision
• Troubles which occurred during impact
• Error times
• Battery voltage
• Energy reserve voltage
• Reference voltage
• Sensor testing results
• Ignition circle error
• Warning lights errors
To get such information it is necessary to contact to car manufacturer.
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Light Bulb Examinations
The lamp examinations is often necessary to determine whether a vehicle has been appropriately
illuminated (did the driver use the lights during the driving, did the driver indicate before he made a
maneuver), or were the stop lights working on the vehicle at the time of the accident.
It is first important to understand how lamps function: the majority in use have single or dual coiled
tungsten filaments suspended on a metallic support. Current passes through the filament which then
becomes hot and emits light. The filament is protected by the glass bulb which contains an inert gas
to prevent oxidation of the coil. The two types of light bulbs have been researched in terms of the
accident investigation and those are the incandescent (left photo) and halogen (right photo).
Photos 98 and 99: Incandescent light bulb and halogen light bulb
There are also high-intensity discharge bulbs and diode bulbs but these two were not thrououghtly
investigated and therefore their examination is not considered in this manual.
Lamp features
The condition of the filament and glass can indicate the events in the lamp’s history allowing
investigators to estimate if the coil was hot at the time of the collision (indicating that the light bulb
was working) or not. The following features are common in examinations:
• Filament coil temperature
The temperature of the coil can reach up to the 2900 0C
• Filament coil deformation
When a coil is hot (illuminating), the tungsten coil becomes ductile and so if the bulb
experiences a strong impact, the coil may deform. Where there is more than one filament in
the lamp (for example dip and full beam headlamps), the deformation of the coils will either
be of a similar magnitude or one coil may be more heavily distorted than the other. In the
latter case, it is likely that one filament is hot and heats the other. The filament that deforms
more is usually the coil that was illuminated. [35]
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Photo 100: The deformation of the coil
• Coil oxidation
If the bulb is broken, the filament will contact air as the inert gas escapes, and if the coil is
hot, the tungsten will oxidize. If the coil is hot but still did not reach the temperature needed
to illuminate, the tungsten may appear tinted with colors ranging from straw to greens and
purples, however if the lamp was lit, the oxides are mostly black, in addition ‘oxide smoke’
may form which is deposited on adjacent surfaces. [35]
Photos 101 and 102: Extreme examples of ‘oxide smoke’ on the light bulb coil
• Coil fracture
Coils may break whilst hot or cold. If a coil is neither conducting nor adjacent to a heat
source, it will be brittle, and may fail by brittle fast failure in the event of a collision. The
following photo is taken from the broken coil under a microscope and it shows the brittle,
clear cut.[35]
Photo 103: Microscopic image of a broken cold light bulb coil
Photo 104: The microscopic image of the coil when it brakes while it is hot (indicating the
melting of the coil in the point of brakeage):
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Photo 105: The melted glass particles on the heated coil creating glass beds on the coil
These evidences need to be collected and further emphasized trough the overall examination of the
vehicle and identification of the other elements that are compatible with the lights (switches, lights
and indicator commands).
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On scene measurement
Note: Without good-quality measurements taken at the time of an accident the analyst is faced with
the need to extract measurement data from incident scene photographs.
Also, the drawings presented in this chapter are the drawings done on a computer for the clarity of
the presentation, not the hand drawings that are usually done on the scene, the hand drawings
would in most cases look like this:
Picture 19: The on-scene hand drawing [48]
Only later will the accident investigator remove the unnecessary measures and produce a scaled on-
scene evidences diagram, which is done with a computer aid and which is making possible the later
measurement of the evidences that were not measured in the first instance.
As soon as the scaled diagram is done and the evidences fixed there is nothing in a 2D that cannot be
measured, 3D measurement will come in later chapters.
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But in order to produce scaled on-scene diagram proper identification of the evidences and proper
measurement of the same evidence must be taken.
The way of producing the on-scene drawing can be described trough the following steps:
• After identifying the evidences draw the road on the paper,
• Input the measures of the road
• Draw the final rest position of the vehicles
• Draw the rest of the evidence leading from the vehicle’s final rest positions to the beginning
of the evidence trail
• Measure the scene and place the measures on the drawing.
“Right angle coordinates” procedure
This procedure is very fast if straight roads, or bends with very big values of the radii, that is basically
making a section where the accident occurred almost straight should be measured.
It requires a fixed line, which is a reference line on which you are measuring the horizontal distance
and lateral distance.
In urban areas fixed point, is used to help position the evidence, but on the open roads, especially in
the desert areas the fixed point can be omitted because it does not make too much of a difference
and it is very difficult to identify.
In the urban areas, for fixed point any element of the fixed object can be used (street light, house
corner, tree, gate corner etc.)
Picture 20: Right angle measurement
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This procedure is very fast and simple and the investigators are encouraged to use it as often as
possible, even when measuring the bends, because it can be combined with the later procedures of
measurement (triangle procedure, curve measuring procedure etc.) and the fixed line of the road
edge is very easy to identify.
It should be noted that the accuracy of the measurement deteriorates with the reduction of the
value of the radii, basically the more curved the road is the more difficult it is to get the right angle
and some differences may appear.
This method can be used any time when an investigator can form a straight enough, fixed line
covering the whole length of the evidences found on the accident scene.
The example of the measurements of the accident scene and the measures acquired by this method
is presented in the following drawing, together with the presentation of the fixed line that is
between the evidences, and the measures are taken along the fixed line and then perpendicular to
the fixed line to the left and to the right.
The location of the fixed line is completely up to the accident investigator, in the presented case any
of the lines of the road could have been used, but the right edge of the road in direction the vehicle
travelled was used to avoid unnecessary movement of the accident investigator on the carriageway
(the example shows that the investigator went on the carriageway to measure only three times,
while all other measurements were done away from the carriageway and therefore the exposure of
the investigator to the traffic on the road was minimal).
Picture 21: Right angle coordinates procedure from the start of the skid marks to the final rest
position
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Triangle measuring procedure
With this procedure two points of reference are selected, where the distance between these points
is known. Each distance to any point can be measured. To reduce the errors during measurement,
the distances must be determined as exactly as possible. The angle between the lines shouldn’t be
obtuse or too acute. If the distance between point A and point B is too long and point C is too close
to the connecting line AB then there won’t be an intersection and point C can’t be found with this
method. An acute angle and inaccurate measurement causes an offset of point C (right picture). [66]
Table 4: Obtuse and acute angle graphical representation
Obtuse angle
Obtuse angle
Acute angle
The points A and B in the next picture form the fixed points. Such points should be points which
can’t be razed easily, e.g. street lights etc.
Picture 22: Triangle measuring procedure
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Measure curves
Chord measuring procedure
At first a fixed point will be chosen from which the curve will be divided into chords. In each case
from the center of the chord in the right angle the height is determined to the trajectory. To
determine the radius of each part of the curve following formula is used:
The procedure would be to place the traffic cones on the beginning, the end and the middle of the
chord, and measure the distance, and then place the cone in the middle of the chord.
Picture 23: Chord measuring procedure-measuring middle ordinate
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After that place the cone on the edge of the road perpendicular to the cone placed in the middle of
the chord and measure the distance between them.
Picture 23: Chord measuring procedure-measuring the chord itself
This method is also the safest method for measuring the curves and it is the only one that the
authors of this book would like to encourage because of the safety of the investigators.
Other methods, presented below are also present but the authors of this manual strongly
recommend avoiding these methods as much as possible, because these methods require
investigator to spend a lot of time on the road.
This method can be used for measuring any curve (skid mark, driving mark etc.), not only the road
bend and the same principle applies for all cases.
Triangulation of curves
The location will be divided into a connected network of triangles, which can be measured. The basic
principle is the triangle measuring procedure which was already described above. To divide an area
into a connected network of triangles is called triangulation. To measure the curve the roadside
should be split up into equal lengths of approximately 5 to 10 meters. Point A and B should be lying
at fixed point like a milestone or something else. Afterwards only the distances to the other points
are measured: B to C, C to D, etc. [66]
Picture 24: Triangulation measuring of curves8
8 Adopted from the PENDANT Accident Reconstruction Guidelines
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Right angle coordinates measurement of curves
With this method a straight line – the baseline, which starts from point B (at the outside of the road)
to point B6 will be marked. In a right angle to this baseline the distances from C1 to A1 and from C1
to B1 will be measured. The distances between B to C1, C1 to C6 and C6 to B6 must not be equal.[66]
Picture 25: Right angle coordinate measurement of curves9
9 Adopted from the PENDANT Accident Reconstruction Guidelines
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Measurement equipment
Picture 26, 27 and 28: Tape measure equipment
Picture 29, 30 and 31: Yardstick
Picture 32: Measuring wheel
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Picture 33 and 34: Laser rangefinder
Picture 35: Total station
Picture 36: Laser scan station
This manual will be focusing on the measurements done by the use of the measuring wheel and
measuring tape, because these are the most common and most reliable tools that investigator can
have (the simple problem with electronic equipment is that it sometimes runs out of batteries,
requires regular maintenance etc.)
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Measuring damages on the vehicles
It is very useful to make as many pictures as possible from damaged vehicles and from accident
scene. Pictures of vehicles should include the damage profile. This includes longitudinal, bonnet,
engine, glazing, wheels etc.
Front and Rear impacts
A datum is set from the undamaged end to either the known length (i.e. for saloon cars investigator
can use 5meters=500 centimeters) or the actual length of the vehicle if the investigator has this data
with him.
The width of the vehicle is divided into 5 equal distances and the measurements are done on the
beginning and the end of each of these segments.
The measurement of damages should be done with the measuring tape in order to get the most
accurate measurements.
Of course, if investigator has a laser rangefinder or a total station it is even better, but the measuring
tape is also quite satisfactory.
For datum lanes investigator can use any stick (preferably yardstick), lane drawn on the ground by
chalk or any other means, as long as it is drawn straight.
The C1 to C6 figures can then be adjusted depending on whether the datum was longer than or
shorter than the undamaged vehicle. Original dimensions could be found the internet or in the
user’s manual for the vehicle-and users manuals are usually kept inside the glove compartment.
Length, height, width, wheelbase distance and other things are available.
Picture 37: Measurement of frontal damages of the vehicle
The same principle of measurement applies for the measurement of the damages on the rear of the
vehicle, but the datum line is then established from the front most point.
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Side impacts
In the case of side impacts the datum line can be established between the undamaged points on the
vehicle and in that case the C1 and C6 measurements are equal to 0. As presented in the following
photo.
Picture 38: Measurement of side damages of the vehicle
Bowed vehicles in side impacts
Bowing is defined as a vehicle which distorts during the impact so that the ends of the vehicle curl
round towards each other.
The damage measurement can be done the same way as with the side impacts without bowing
(determining the datum line at the undamaged points) or by determining the datum line from the
other side of the vehicle, and measuring like in the case of the frontal damage.
Photo 106: The measuring of the crush depth with the usage of the 4 measuring tapes
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Photographing and filming the traffic accident evidence
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The Accident Scene Photography is a part of Forensic Photography with main purpose to provide
accurate, photographic record of an event, after-the-fact, for the benefit of further investigation or
other legal proceedings. Accident scene photography together with on-scene measurement and
exclusion of traces and object from the scene is also one of the methods for securing evidences from
the scene of the accident which complement each other.
Photo cameras and lightning
Digital photo camera
Today we know two basic categories of photography: Digital and Analog photography, but because
of reliability and characteristics of digital photo cameras, we will elaborate only digital photography.
Digital photo camera creates an image using an electronic photo sensor which contains millions of
photosensitive diodes. Quality of digital photography depends mostly on size of electronic sensor
which is measured in pixels (bigger electronic sensor means more pixels and therefore better and
more detailed photos). Only two types of electronic photo sensors are in use today: CCD (Charge
Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor).
Picture 39: Different sizes of photo sensors today
In order to create an image, it is essential that sufficient amount of light to be brought to an
electronic sensor and this light must be focused in order to create a sharp image on the sensor. This
can be accomplished only by adequate system of lenses and shatter mechanism of the camera.
Picture 39: Parts of the camera
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Camera lenses
Main role of camera lenses is to bring sufficient amount of light to electronic photo sensor and
create a sharp image of the photographing object on the electronic photo sensor. In order to do so,
camera lens has two main parts: System of optical lenses and Aperture mechanism.
Picture 40 and 41: Cross section of camera lens and aperture mechanism
Purpose of the System of Optical lenses is to create sharp image of the photographing object on the
electronic photo sensor, and Aperture mechanism regulates amount of light that will reach
electronic photo sensor.
System of Optical lenses
Optical lens is transparent body limited by two spherical surfaces or one spherical and one plane
surface. According to the method of refraction they are divided to convergent (collective) and
divergent (dissipative) lenses.
Picture 42: Converging and diverging lenses
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In order for sharp image of the photographing object to be created on the electronic photo sensor,
multiple lenses are needed (both convergent and divergent) to be lined up in specific order which
ultimately creates a system of optical lenses which provides adjustable focal length and therefore
focusing an image of the photographing object on variable distances from the camera.
Picture 43: Different focuses of camera
NOT FOKUSED IMAGE FOKUSED
Aperture mechanism
Unlike focusing the image of the photographing object where all other objects which are closer to
the camera or further away of it appears blurry, system of camera lenses together with aperture
provides another ability of camera-Depth of Field. Depth of Field (DOF) represents the ability of
photo camera to simultaneously adjust the focus on objects at different distances from the camera.
Greater depth of field means that sharp objects can be seen on a large range of distances from the
camera.
Photos 107 and 108: Camera without the adjusted depth of field and with adopted depth of field
The Aperture mechanism of the camera lenses situated close to the connecting point between
camera lens and the camera body. The role of the aperture is to determine the amount of light that
will pass through the lens and to provide the depth of field. The aperture mechanism is composed of
94
number of thin metal sheets which can be expanded and/or contracted, thus increasing or
decreasing the hole through which light passes. When the larger the aperture higher amount of light
passes to the sensor and vice versa. The aperture of photo camera is marked by small letter “f” and
set of numerals (i.e.1.4, 2, 2.8, 4, 5.6, 8 etc.).
Picture 44: Different aperture sizes
Smaller f-number represents larger aperture, and vice versa (numerals of aperture may differ
depending on type of apparatus but in any case each number represents doubled size of aperture).
Higher Depth of field is achieved with a smaller aperture.
Camera body
For clear image to be created on photo sensor it is essential for sensor to be kept in absolute
darkness prior and after allowing desired amount of light to be passed thru the camera lenses, which
is the main purpose of camera body (lat. camera obscura). The amount of light that will reach photo
sensor is regulated by shutter mechanism of the camera body, and if natural source of light is
inadequate (night photographing conditions), artificial source of light (flash) can be mounted on
camera body.
Shutter mechanism
The shutter is a mechanical device that does not allow light to penetrate through the lens in the
camera body. Pressing the shutter release button or lever shutter, the shutter is opened for a short
period of time which can be adjusted. Length of time in which the shutter stays open is called the
exposure time. If the photographing object is poorly lit it takes a long exposure time for sufficient
amount of light to reach photo sensor, and vice versa. Exposure time is indicated in seconds and it is
common that each step represents doubled amount of time. The default value of the exposure:
1/4000, 1/2000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1, B, T (all values are in
seconds, where letter “B” represents exposure while the shutter button is pressed (so-called Bulb
Mode), and letter “T” - the exposure lasts until the shutter is pressed a second time (the Toggle
mode)-both modes are used with very poor lightning conditions).
Picture 44: Photos with Short, Normal and Long exposure times
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Typical standard value for the duration of the exposure is 1/125s for pictures taken in sunlight. Of
course, the optimal value depends on the aperture, brightness and dynamic scenes, the desired
depth of field and some other factors. For the same aperture, we will need to adjust a longer
exposure time in poor lighting conditions, and vice versa.
ISO Number
Another important feature of digital photo camera is ISO number. ISO is an acronym for the
International Standards Organization. ISO numbers tell you how sensitive a digital photo camera is to
light. This is a sequence of some of the most common ISO numbers available with digital cameras
today: ISO 100 200 400 800 1600 etc. A low ISO number is not very sensitive to light, which means
that aperture and shutter speed must be adjusted to let more light onto the camera’s image sensor.
Low ISO numbers result in images with less noticeable grain. A high ISO number is more sensitive to
light, which means that aperture and shutter speed must be adjusted to reduce the amount of light.
High ISO numbers produce photographs with noticeable grain.
Picture 46: Photos taken with same aperture and exposure time but different ISO number
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On scene photography
Considering that the modern digital cameras allow the investigator to make a large number of
photographs this advantage should be taken and the investigator should take as much as possible
photographs on scene.
One important thing for the investigator to bear in mind is that photographing should be done in a
systematic way and with a beginning to end walkthrough the accident scene.
The photographs must be taken for the all approaches, starting with the wider view of the accident
scene to the final rest position of the vehicle.
For the single vehicle accidents it is easy and straight forward, as the investigator needs to follow the
movement of the vehicle and take the photo in a certain interval, and of course, to take a few
photos from the opposite side.
Picture 47: Camera positions during the on-scene investigation in a single vehicle accident
While taking the photos of the wider views, and approaching the final rest position of the vehicle,
the investigator will reach certain evidences and marks, and these should be also photographed with
a close up, while keeping the order of the photos. So the investigator should take the photo of the
wider view, and when he reaches the beginning of the skid marks for instance, take the close up
photo of the beginning of the skid mark.
For the accidents with more vehicles the same principle applies, just the investigator needs to follow
the path of every vehicle that participated in the accident.
When it comes to the accidents with pedestrians, the more detailed description will be presented
further in the manual, but the investigator should also follow the path of the pedestrian alike path of
the vehicles.
Following the path of an animal in animal collisions is not mandatory, and it is mostly the case that
the investigators do not follow it, except in cases where it is important to prove the actual reason for
the animal to appear on the road.
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Table 4: The example of the single vehicle accident photographs
The view of the beginning of the
interchange exit
The wider view of the accident scene
location
The wider view of the accident scene
location, on the approach to the point
where the vehicle started to leave scratch
marks
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Close up on the beginning of the scratch
marks
Additional close up on the scratch marks
Wider view on the area where the
vehicle went off road to the left
After these photos, investigator must also make the close up photos of the other evidences that can
be found on the scene, vehicle damages photographs etc.
The photos of the vehicle damages that should be taken are shown in the following diagram:
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Picture 48: Camera positions for photographing the vehicle damages
The previous diagram shows that the photos that must be taken are the four wide photos of all
vehicle sides, with additional photos of the actual vehicle damage.
However, these are not the only photos that the investigators should take regarding the vehicle, as
the photo evidence is the one evidence that is the least biased and also the easiest to take.
The additional photos that the investigator should take regarding the vehicle are:
• Photos of the wheels and the tyres,
• Photos of the lights and indicators,
• Photos of the vehicle interior,
• Photos of the seatbelts,
• Photos of the dashboard and speedometer
• Photos of the seats etc.
All these photos, combined with the ones of the road and on scene evidence, and compared with
the other on scene activities and measurements that the investigator is making create a full on-
scene investigation documentation, and help the further investigation and analysis trough the
application of the three principles: comprehensiveness (or the principle of the overall scope),
Principle of objectiveness and Principle of compatibility.
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Investigation of the road design and construction elements
101
Road design elements
The road design is governed by different laws and standards and the purpose of these standards is to
provide the basic elements for the successful design of the road scheme that will provide mobility,
capacity and safety for the various road users.
In the Sultanate of Oman the Oman Highway Design Manual is the governing standard, but it also
allows the engineering judgment and therefore puts the responsibility on the design institution to
provide the safety trough the design.
Investigator is not obligated to know the design standards, but should feel free to use their
reference whenever possible.
Oman Highway Design Manual stipulates:
Therefore investigator should always determine the posted speed limit on the road, later
investigation can also determine if the posted speed limit is in accordance with the given standard
but by determining the posted speed limit, as it is said in the Oman Highway Design Manual,
paragraph 4.2.3.1 investigator determines the maximum safe allowable speed on a road in normal
conditions. The easiest way to determine and confirm the posted speed limit is by photographing
the traffic sign indicating the speed limit and identifying its position in relation to the traffic accident
area and the road user travel path.
Picture 49: The speed limit sign position confirmed by photo, and the on-scene diagram in relation to
the traffic accident location
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Next important thing is to determine if the road user was notified about the hazard or the hazard
appeared as unexpected.
One of the easiest ways to inform the road users about the hazards is by the traffic signs and
markings.
According to the current traffic law the warning signs warn the drivers about the danger ahead, and
the Oman Highway Design Manual stipulates:
Therefore determining the location of the traffic signs in relation to the traffic accident location is
essential for later determining the liability for the accident.
The investigator should try to drive along the path of the vehicles that have collided in order to
determine what the drivers were able to see and were informed of.
The recommended distance would be 500m as any information given prior to this would be difficult
to influence the actual accident.
Also investigator should try to walk the path the pedestrian was using until the point of collision with
the same intent of determining what was the pedestrian able to see and was informed of.
One of the very important elements is the temporary traffic management in the work zones, as this
is a temporary measure which is standardized and the drivers are considering it as a hazard.
Therefore the investigator should determine the location of all of the temporary traffic signs, way
the traffic was regulated and the work zone protected and also ask for the design of the temporary
traffic management scheme and compare it with the evidence determined on-scene.
Picture 50: The position of the temporary traffic signs on the scene of the accident
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Picture 51: The location and the position of the traffic signs required by the standard
Therefore it is easily determined if the company that was performing the road works provided a safe
and as per the standard temporary traffic management or they sacrificed the safety due to the
different reasons (budget, lack of knowledge, urgency etc.)
Also, the road designs are often delivered to the police for the revision, or kept as a reference in
different government institutions, and therefore are available for the investigator.
If the investigator is able to acquire these designs he should check the constructed layout against the
designed layout and determine if the construction was don as per the design.
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With the use of the computers and the obligation of the design institution to provide the soft copy of
the designs for the revision the investigator can have a database of the designs and bring the design
layout to the scene of the accident. This can be very helpful in on scene investigation as the drawing
pad used can be a proper design drawing instead of the blank paper, as presented in the following
drawings:
The important thing is not to consider the designs as absolute and all of the measurements must be
taken as if there is no drawing, this is only to make the investigation easier, not to replace it.
The difference in the constructed road layout and the designed road layout should be presented in
the report as it can change the values of the design speed and therefore the safe speed. During the
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on-scene investigation elements of the road surface that could influence the driver’s driving or the
vehicle’s movement should also be identified and referenced to the actual scene of the accident.
These elements can be different changes in the road layout or construction, like damages, sand
dunes, debris, potholes etc.
Photo 109: The pothole that can influence the driver in terms of making the decision to change his
position on the road
The damaged road edge can influence the sudden change in the friction force on the wheels on the
same axle and therefore influence the vehicle’s movement and initiate the driver’s reaction.
Photo 110: The damaged road edge
The damaged road edge is especially important if the design standards require the shoulder to be
asphalted, but due to the budget limitations the decision was made not to comply with the
standards. This is something which brings the additional light on the profession of the investigator
and that is identifying the problems that contribute to the reduction of the level of traffic safety.
106
Characteristics of rollovers on-scene investigation
107
Picture 52: The axis of the vehicle and its movement along the axis
During the vehicle movement forces along all the axes influence the vehicle. Lateral forces are the
ones that influence the vehicle to lean to one side or the other and eventually rollover if the lateral
forces increase beyond the point of the lateral stability of the vehicle.
Vehicle stability depends on several factors, but the main focus in this manual will be on the height
of the center of gravity (center of mass) and the difference in friction factors on the wheels of the
same axle.
As presented before the main traces found on the road of the rollover accident are the skid marks
with striations.
The measurement of these skid marks is specific due to the need of determining the radii of the skid
marks at the beginning of skid.
The measurement of the radii is the same as the measurement of the curve presented in the earlier
chapter, with the emphasis on the beginning of the skid marks considering that this is the point
when the driver lost control of the vehicle.
After arriving on the scene the investigator should identify the origin of the skid marks.
Lift
Yaw
Pitch
Slide
Move
Roll
108
Picture 53: The origin of the skid marks in relation to the vehicle’s wheels
Picture 54: The measurement of the skid mark arc radii
It is recommended that the C value is approximately 15 meters if the skid marks length allow for this
distance to be measured. The skid mark generated by the front near side wheel is usually the most
distinctive and therefore easies to measure.
Investigator should also determine the actual cause of the rollover, which can be the increase in the
vehicle’s momentum to the point where the vehicle leans to one side beyond the tipping point or
the vehicle has hit some obstacle with its wheels or wheel and therefore this obstacle (usually curb)
is the reason for the vehicle to lose its stability and start to rollover.
Also, common in the desert environment and when the vehicle is skidding sideways off road on the
gravel or sand surface, the accumulation of the sand on the side walls of the wheels which in some
Near side front
Near side rear
Off side rear
Off side front
109
point time rises to the point where it become the obstacle that initiates the loss of stability and
rollover.
The following photos present the common evidences for the starting point of the rollover:
a) If a vehicle hits a curb (Photo 111)
b) If a vehicle rolls over due to the increase of the momentum caused by the change in terrain
height (Photo 112)
c) If a vehicle rolls over due to the accumulation of the sand or gravel on the side walls of the
tyres (Photo 113)
110
Also important element that needs to be determined is the vehicle’s dimensions, as they influence
the roll stability of the vehicle.
If possible investigator should measure the vehicle dimensions on scene, but due to the position of
the vehicle it is sometimes not possible to do the measurement until the vehicle is returned back on
the wheels.
The main dimensions that the investigator should measure are:
• The track width (Photo 114)
• The height of the vehicle with the load (Photo 115)
Photo 116: Measurement of the road slope (it also influences the stability of the vehicle and the safe
speed for negotiating the bend)
111
When it comes to the heavy vehicles and tankers the measurement of the rear wheels should be
done to the middle of the space between the wheels on the same axle.
Photo 117: Measurement of the axle width of heavy vehicle
The presented measurement is the actual track width for the heavy vehicles (different to the track
width of the light vehicles) as presented in the simplified model of a heavy vehicle in a steady turn,
in which the vehicle, its tyres, and suspension have been presented into a single roll plane.
Picture 55: The dimensions of a heavy vehicle and influencing forces while making a turn
Also, tankers are especially prone to rollover due to the load shift, and therefore investigator should
determine the quantity of the liquid inside the tanker in relation to the actual tank capacity.
This is important to determine the possibility of the load shift as it reduces the safe speed for
negotiating the bend with a tanker.
112
Picture 56: Moving of a liquid inside tanker while it is negotiating the bend
Unfortunately, there are no means at the moment to measure this load shift after the accident and
the only thing the investigator can do is to determine the load/capacity ratio.
This information can be found in the loading manifest.
One of the common errors of the drivers of heavy vehicles is cutting short on the turn, thus causing
the rear tandem axles to go off to the soft shoulder or a ditch therefore creating a sudden change in
vehicle’s center of gravity position which can result in the tip over or a rollover.
The evidence of this can be found on the curbs (as the tyre wiping mark) or on the gravel or soil as
the driving mark.
Photo 118: The position of the wheel and the curb in the point where the accident was initiated
(point of no escape):
The role of the load shift in the vehicle stability is not only significant in the cases of the tanker
trucks, as you can see in the following photos (119, 120 and 121) from the TRL conducted test:
In this case the load shift happened with the wooden logs being the load, as the lateral movement of
the logs was only restrained by the friction between the logs and the logs and the platform.
113
Characteristics of pedestrian and animal collision on-scene
investigation
114
Pedestrian accidents
Main types of pedestrian collision are:
Wrap Trajectory
The most common type of pedestrian collision, which usually involves a decelerating vehicle. In this
type of collision, the pedestrian’s torso wraps up onto the vehicle’s hood.
Picture 56: Wrap trajectory diagram
Forward Projection
This is the most common type of pedestrian collision that occurs when the pedestrian’s center of
mass is lower than the leading edge of the vehicle.
Picture 57: Forward projection diagram
Fender Vault
This type of collision involves both vehicles which are braking and non-braking. The pedestrian is
contacted near an outboard edge: the torso is wrapped onto the hood of the vehicle, and the
pedestrian exits off of the side of the vehicle.
Picture 58: Fender vault diagram
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Roof Vault
This type of pedestrian collision occurs when a pedestrian center of mass is higher than the leading
edge of the vehicle. The pedestrian is lifted into the air because of the vehicle’s speed or a low roof
line. Typically, these types of pedestrian collisions are caused by high impact speeds.
Picture 59: Roof vault diagram
Somersault
This is the least common of pedestrian collisions and is due to high impact speeds. The pedestrian is
flipped into the air (or is somersaulted) before striking the ground.
Traces to search for in the pedestrian accidents
The usual traces that can be found in the pedestrian accidents are:
• The final rest position of the pedestrian’s body which is indicated by the different biological
traces and even traces left by the medical personnel when they were providing the medical
assistance on site (in the case the pedestrian body is moved).
Photo 122: Biological traces indicating the final rest position of pedestrian’s body
• The injuries on the pedestrian and the compatible damages on the vehicle
Picture 60: The simulation of the pedestrian impact done by the Legal Arsenal
116
The damages on the vehicle should be marked and identified, together with the remains (if
any) of the biological traces originated from the pedestrian on the vehicle chassis,
windscreen etc.
Photo 123: The damages identified on the vehicle from pedestrian impact
The biological traces (usually human hair and parts of skin) should also be clearly identified
and presented in relation to the damages of the vehicle
Photo 124: The hair from pedestrian impact on the windscreen
And the position of the vehicle and the pedestrian and the vehicle can be re-enacted by
using the colleague or other person at the scene and photographing them in different
positions the investigator considers as the positions of the accident participants at the point
of impact.
Photo 125: The re-enactment photo of the position of the vehicle and pedestrian in the
point of impact
117
• The final rest positions of the parts of clothes or the items that the pedestrian was carrying
Photo 126: The identification of the final rest position of the items pedestrian was carrying
The pedestrian collision usually leaves distinctive evidence on the vehicle when the collision happens
in a way that the pedestrian is hit by the front of the vehicle. These deformations on the vehicle
must be identified and measured.
Photos 127 and 128: The measurement of deformations on the vehicle generated from the
pedestrian impact
But in some cases the collision happens when the vehicle is going in reverse and in this case the
evidences of the point of collision are more difficult to find, especially in the cases when the vehicle
is a heavy vehicle. This is due to the material used to build the rear of the vehicle is usually steel and
the most common evidences that will indicate the point on the vehicle that collided with a
pedestrian are the wiping marks of dust on different parts of the vehicle.
Photos 129 and 130: The whipping marks from pedestrian identified on the vehicle
118
Sometimes these wiping marks are very difficult to present even with a photo, and therefore it is
recommended that the investigator points them out with some distinctive pointer and numerates
the evidence when taking the photos.
In the case of the vehicle moving in revers very important evidence is the positions of the rearview
mirrors and the driver’s view onto these mirrors (what was driver able to see by using the mirrors):
This is done by the investigator sitting into the driver’s seat and photographing the mirrors so that
the image on the mirrors shows the driver’s field of view.
Photos 131, 132 and 133: The available field of view for the driver provided by the rearview mirrors
119
Impacts with camel and other animals
The dromedary camel is one of the two largest living camels. Adult male dromedaries grow to a
height of 1.8–2 m and females to 1.7–1.9 m. The weight is usually in the range of 400–600 kg for
males and 300–540 kg for females. Very large male Dromedaries, however, can weigh as much as
1,000 kg
There are not a lot of researches on the collisions between the camels and the vehicles, and
therefore the research of the vehicle to moos or elk collisions reference will be used in this manual.
Due to the height of the camel, if it is hit by the light vehicle its upper body is usually directly hitting
the vehicle cabin and crushes the roof of the vehicle.
Photos 134, 135, 136 and 137: The elk crush test with the Peugeot 407 colliding with the test dummy
(a sequence of the impact of the light vehicle with a camel like animal)
The slow motion camera then captures the influence of the camel’s weight on the vehicle, and the
following photos show that the weight of the camel is transferred onto the vehicle chassis and to the
rear wheels of the vehicle (the suspension of the rear wheels is therefore influenced and the rear of
the vehicle is pushed down and then back up).
Photos 138 and 139: The influence of the camel body on the vehicle movement during impact
120
For this reason the braking marks of the vehicle in the point of the collision with a camel could be
expected to increase their intensity (in the point of the maximum influence of the camel’s weight on
the vehicle) and after that reduce the intensity or even lose the contact with the ground and the
investigator should search for this kind of disturbances in the vehicle’s skid or braking marks to
determine the actual impact area.
If there are no braking marks the investigator should search for a short, appearance of the skid mark
and even a scratch mark, as it is quite possible that the rear fender of the vehicle has impacted the
ground at the time of the maximum influence of the camel’s weight on the vehicle.
Also, the area of impact can be identified by the glass debris spreading from the vehicle’s windshield,
as it is also pushed back by the volume of the camel’s body.
Photo 140: The glass debris pushed back by the camel body
Area of the impact is also usually indicated by the loss of control of the vehicle and sudden change in
direction of travel.
Loss of control is usual in the camel accidents with the light vehicles as the driver and the occupants
are directly impacted by the whole upper weight of the camel’s body which lands on the vehicle
usually at the end of the bonnet and the height of the A pillar.
Photo 141: The damage on the light vehicle caused by the impact to the camel at high speed
121
In these cases investigator should determine the initial point of impact on the road, and also the
initial impact area on the vehicle which is indicated by the damage on the vehicle and the biological
traces (fur, skin and blod) transferred from the animal onto the various parts of the vehicle.
Photo 142: The camel fur that remained on the vehicle after the impact
The position of impact can be determined if there are the evidences of the animal’s hooves
scratches on the road and the beginning of the scratches indicates the point in which the animal was
at the time of the accident.
Sometimes these marks are not existent as the animal reacted by jumping onto the vehicle or the
force of the impact was not enough to leave the hooves’ scratch marks.
The problem with the camel collision investigation is determining the actual position of possible
perception, as in a lot of cases the people do not even realize the existence of a camel close to the
road and the driver’s reaction is either too late or even the driver does not have the time to react.
Picture 61: The driver’s view onto the road and the camel standing close to the road enough to pose
a hazard (camel 200m and 100m away)
The first image is the driver’s view onto the road 200m before the position of a camel and the
second photo is the driver’s view onto the road 100m before the position of the camel indicating in
both cases difficulty to recognize the existence of the camel and mistake it for some rock, sand dune
etc. The investigator should try to drive down the road from the same approach the driver was using
and film the approach in order to later analyze the possibility of the driver to realize the hazard.
122
Using software and additional resources
123
There are many on-scene investigation and accident reconstruction packages available on the
market, and the investigator can use any of them for the actual investigation freely.
The main focus in this manual will be on the commonly available software and the possibility of its
use in the traffic accident investigation.
The easiest to use and freely available is Google Earth.
Google Earth provides the means to measure accurately enough location of different elements of
the road in relation to the accident location.
Google Earth also provides means to determine the slope of the road and the location of the
obstacle which cannot be easily measured (hill, rock etc.)
If combined with other software it can help the investigator to do the post measurements, especially
if the accident has taken place on a busy street and the investigator was not able to perform all the
measurements due to the time constraint or any other reasons that might arise.
Picture 62: The measurement of the bend radii done by the use of the Google Earth as a mean to
confirm the on-scene measurement
Google Earth can also be combined with the road design software and the profile or even the cross-
section slope can be obtained from the data provided by the Google Earth.
Of course, investigator should bear in mind that Google Earth is only help not the replacement for
the on-scene measurement.
Also, based on the field measurements, and by using the software for drawing or even accident
reconstruction, the investigator could determine different elements of the accident that are not
124
possible to measure, like the encroachment of the vehicles onto the traffic lane for opposing traffic
at the time of collision, especially if the gauge marks are found on the center line.
Photo 143: The gauge mark on the centre line indicating the point of collision
The procedure would be the following:
• Measuring the on-scene evidence and the damages on the vehicle
• Locating the gauge mark on the road and determining the causation of the gauge mark
(which part of which vehicle made the mark itself)
• Determining the vehicle dimensions and creating the vehicle top view models
• Positioning the vehicles in the point of collision in relation to one another
• Positioning the vehicles on the road in the point of collision
Picture 63: The vehicle positions in the point of collision
125
Modern day vehicles have also GPS units that can give the Easting and Northing locations of the
vehicle in point of time, from this information investigator can easily determine the speed of the
vehicle if there is second-by-second information:
Picture 64: The location data from the satellite tracking and its representation in a diagram of vehicle
movement
From the previous images the vehicle position on the road was determined, the relation of the
vehicle position to the centerline was determined and the speed can be determined and also the
way the driver was driving and his reaction, as it shows that the driver steered to the left, and
started to decelerate.
Of course, this kind of information might seem powerful and the people might consider that the
need for the on scene investigation is minimized by the use of these kinds of software and data, but
the investigator should always remember that this is not the Universal solution as the accuracy and
the availability of the GPS data is not always to the meter even.
And also the GPS data can provide false information on the vehicle movement and position.
126
Picture 65: GPS data showing the various positions of a stationary vehicle as a result of the
inaccuracy of the GPS
The GPS data actually shows the lot of movement, which is only a consequence of the GPS unit
acquiring the satellite connection, and in reality the vehicle was stationary.
Also, the GPS data provide only a point, investigator should never forget that the vehicle has its
dimensions and it is never a small point, but can rather be quite large object.
Therefore the position of the GPS unit on the vehicle can play a significant role, as shown in the
following picture.
Picture 66: The difference between the GPS unit being positioned under the driver’s seat and under
the passenger seat
Basically, GPS unit does not go over the centerline but based on the position of the GPS unit in the
vehicle the driver is either complying with the law or encroaching onto the traffic lane for the
opposing traffic.
Therefore the GPS data can be viewed and collected only as the part of the evidence.
127
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Traffic Accident Investigation Guidelines
With Reference to Desert Environments
Authors:
Sasa Kocic i Zoran Stojanovic
Contributor:
David Marsh
Publisher:
Medjunarodni institut za bezbednost
International Security Institute
For the publisher:
dr Orhan Dragas
Reviewers:
dr Demir Hadzic
dr Dejan Jovanov
Language:
English
Print:
Goragraf Beograd
Year
2014
Circulation:
500 copies
133
CIP – Каталогизација у публикацији Народна библиотека Србије, Београд
656.1.08 625.711.82
КОCIĆ, Saša, 1970- Traffic Accident Investigation Guidelines
with Reference to Desert Environments / Saša Kocić, Zoran Stojanović. - Beograd : Međunarodni institut za bezbednost, 2014 ( Beograd : Goragraf ). - 131 str. : ilustr. ; 25 cm
Tiraž 500. - Abouth the authors: str. 4. – Traffic accident terminology: str. 8-9. – Bibliografija: str. 127-131.
ISBN 978-86-89899-00-9 1. Stojanović, Zoran, 1976- [аутор] а) Друмски саобраћај – Безбедност b) Саобраћајне несреће - Увиђаји COBISS . SR – ID 206249228
