Car-Truck StudyCar-Truck Study

PublishedPublishedApril 2002April 2002

Purpose of StudyPurpose of Study

To examine unsafe driving actions (UDAs) that contribute to fatal crashes between cars and large trucks (over 10,000 lbs) and to identify instructional strategies.

BackgroundBackground

5,211 killed and about 140,000 injured in crashes involving trucks (>10,000 lb) in 2000

98% of these fatalities and injuries in passenger cars

25% increase in trucks registered in last decade

40% increase in truck VMT in last decade

Are poor judges of speed, maneuverability, braking, acceleration of trucks

Assume operation of car and truck is same

Do not recognize risks associated with driving near trucks

Literature Suggests Many Car Drivers…Literature Suggests Many Car Drivers…

Need Better Understanding of Driver Need Better Understanding of Driver Actions Preceding Car-Truck CrashesActions Preceding Car-Truck Crashes

Information on UDAs is in crash data files

Inherent uncertainty Police judgments, witness statements, crash

survivors

Straightforward tabulations and associated statistical techniques inadequate

ObjectivesObjectives

Examine recorded unsafe driver actions

Identify unsafe driver actions more likely in car-truck crashes than in car-car crashes

Discern behavioral patterns associated with these actions

Suggest educational interventions

MethodsMethods

Estimate likelihood of particular UDA being recorded in a car-truck crash – relative to a car-car crash.

Examine in detail crashes with UDAs that are more likely in car-truck crashes.

Vehicle Crash DataVehicle Crash Data

NASS General Estimates System – GES– All severity levels– Complex sample

State crash data files– All police reported vehicle crashes in state– Each state is different

Fatality Analysis Reporting System – FARS– National – All fatal vehicle crashes

Data SelectedData Selected

FARS Trucks in Fatal Accident File (TIFA)

– At UMTRI

– Detailed- including police accident reports

Limits analysis to fatal crashes

Driver-Level Related Factors in FARS Driver-Level Related Factors in FARS

(up to 4 Per Driver Can Be Coded)(up to 4 Per Driver Can Be Coded)

Failure to keep in lane Failure to yield right of way Driving too fast for conditions

or in excess of posted speed Inattentive Operating vehicle in erratic,

careless or negligent manner Driving on wrong side of road Non traffic violation -

homicide Sliding due to ice, water,

slush

Passing with insufficient distance

Making improper turn Drowsy, sleepy, asleep,

fatigued Overcorrecting Improper of erratic lane

change Following improperly 94 codes

Major FindingsMajor Findings

Car drivers are more likely to commit unsafe driving acts than truck drivers

Unsafe driving acts for fatal car-truck crashes are very similar to those for fatal car-car crashes

Of all 94 unsafe driver acts, 5 actions account for 67% of the unsafe acts by car drivers

The same five unsafe driving acts were also the most common factors for truck drivers, accounting for 51% of unsafe acts by truckers

Distribution of Driver Factors for Distribution of Driver Factors for Drivers in Fatal Car-truck CrashesDrivers in Fatal Car-truck Crashes

19.7

45

26.8

7.90.7

73

167.7

2.9 0.40

10

20

30

40

50

60

70

80

% D

rive

rs

Car drivers Truck drivers

01234

10,732 car drivers10,732 truck drivers

# FactorsPer

Crash

Car Drivers Are More Likely to Commit Car Drivers Are More Likely to Commit Unsafe Driver Acts Than Truck DriversUnsafe Driver Acts Than Truck Drivers

Of all UDAs identified, 75% were assigned to car drivers and only 25% to truck drivers

80% of car drivers in the sample were assigned at least 1 UDA compared to 27% of truck drivers

Five Most Frequent Driver Five Most Frequent Driver FactorsFactors

0102030405060708090

100

car-car car-truck

% o

f d

rive

r fa

cto

rs

inattentionfail obey tcdspeedingfail yield rowfail keep lane

100% = 61,466 for car-car crashes = 17,867 for car-truck crashes

UDAs Similar Between Fatal Car-Truck UDAs Similar Between Fatal Car-Truck Crashes and Fatal Car-Car CrashesCrashes and Fatal Car-Car Crashes

This finding implies that effective programs to promote safe driving in general can also be used to promote safe driving near trucks.

However, it must be emphasized that mistakes around trucks can have much more severe consequences.

Five UDAs Account for Most Five UDAs Account for Most Unsafe ActsUnsafe Acts

Failing to keep in lane (21%) Failing to yield right of way (16%) Excessive speed (12%) Failing to obey traffic control devices

and laws (9%) Inattention (8%)

Five Most Frequent Driver Factors Five Most Frequent Driver Factors Car-truck CrashesCar-truck Crashes

0

5

10

15

20

25

30

car drivers truck drivers

fail keep lanefail yield rowspeedingfail obey tcdinattention

100% = 13,393 for car drivers = 4,474 for truck drivers

Same Five UDAs Also Most Common Same Five UDAs Also Most Common Factors for Truck DriversFactors for Truck Drivers

Failing to keep in lane (12%)

Failing to yield right-of way (14%)

Excessive speed (11%)

Failing to obey traffic control devices and laws (8%)

Inattention (6%)

Detailed Review of Fatal Detailed Review of Fatal Car-truck Crash RecordsCar-truck Crash Records

Selected sample of over 500 fatal car-truck crashes with one of the 4 driver factors from FARS 1995-1998

Obtained crash files from TIFA records from center for national truck statistics

Reviewed for behavioral sequences, driver characteristics, other actions/conditions

Results From Detailed ReviewResults From Detailed Review

Crashes in which car driver was drowsy, asleep, fatigued or following improperly - male car drivers more likely than female

Male and female car drivers equally likely in fatal crash in which they made improper lane change or in which their vision was obscured

Younger car drivers- more likely to be drowsy, asleep, fatigued

Older drivers - more likely to have obscured vision Younger truck drivers – more likely than older to

follow too closely

Results From Detailed Review Results From Detailed Review

Younger car drivers - alcohol, speed Older car drivers - failure to yield right-of-way,

improper turns, intersection problems Younger truck drivers – more likely than older

alcohol, speed, drugs (number of cases small)

ConclusionsConclusions

Unsafe driver actions in fatal car-truck crashes attributed more to car drivers than to truck drivers

Driver-factors in fatal car-truck crashes consistent with broader crash risks

Most driver-related factors equally likely in fatal car-truck and car-car crashes

Profile of causes and characteristics of fatal car-truck crashes similar to those for car-car crashes

Important LimitationsImportant Limitations

FARS data is based on police reports

Potential survivor bias (98% of deaths are car occupants)

Study is based on fatal crashes only

Only two-vehicle crashes in sample

Very difficult to determine “causality”

The Good NewsThe Good News

When driving near large trucks, car drivers are largely in control of their own safety. Car drivers who know the characteristics of large trucks and drive accordingly are likely to be safe.

What Next?What Next?

Teach drivers about trucks Stopping distance, blind spots, turning characteristics...

Teach car drivers about 5 unsafe actionsFailing to keep in lane

Failing to yield right-of way

Excessive speed

Failing to obey traffic control devices and laws

Inattentive

What Next?What Next?

Emphasize share-the-road strategies

Await results of DOT’s Truck Causation study

The AAA Foundation for Traffic Safety is a 501(c)(3) public charity located in Washington, DC that is dedicated to research and education about the causes of traffic crashes.

It is supported by by donations from AAA/CAA Clubs, AAA/CAA members, and other organizations associated with the American Automobile Association/Canadian Automobile Association.