Large Truck Crash Causation Study

Ralph Craft, Ph. D.Federal Motor Carrier Safety AdministrationU.S. Department of TransportationMay 2006

Whats Cause?Websters Cause \koz\ n. 1: a reason for an action or condition 2: something that brings about an effect or a result .

In other words: If A, then B.

Defining LTCCS Cause

LTCCS Cause \koz\ n. 1 a: factors that increase the risk of a crash such as driving behavior, vehicle problems, road and weather conditions b: something that does not usually result in a crash but increases the chance of a crash

Dispelling the Myths

In 71 percent of fatal 2-vehicle fatal large truck/other-vehicle crashes, police reported one or more driver factors for the other vehicle, but none for the truck driver. (1996 FARS, NHTSA)

Passenger vehicle drivers are at fault 70 to 80 percent of the time in truck-car crashes. (Truck Line Express, 7/28/2005)

FARS data: not CausationNHTSA: driver factors in FARS are not the causes of crashes, becauseData are coded by FARS analysts away from crash scene based on written reportsSome factors are not reported on reports FARS analysts use

Primary Sampling Units

Coding LTCCS CrashesCritical Event: the event after which the crash is unavoidableCritical Reason for Critical Event: the immediate reason for critical event Not the necessarily the cause of the crashCrash Associated Factors: All factors that could be important in explaining why the crash happened

Critical EventSUV turns leftCritical ReasonDriver inattentionAssociated FactorsCrash Example

Critical Events All TrucksEventsNumber %Over lane line or off road25,00032%Loss of control (speeding, etc.)22,00029%Other vehicle in Lane18,00023%Turning, crossing intersection 8,00010%Other (pedestrian, fire) 4,000 6% Total77,000 100%Critical Event not coded to truck64,000

Critical Reason Trucks, all CrashesREASONSNumber%Driver Non-Performance (sleep, sick) 9,000 12%Driver Recognition (inattention) 22,000 28%Driver Decision (speed, aggressive) 29,000 38%Driver Performance (overcompensate) 7,000 9%Vehicle 8,000 10%Environment (roadway, weather) 2,000 3% Total 77,000 99%Critical Reason not coded to Truck 64,000

C. R. Truck / P.V. CrashesCritical Reasons TrucksP.V.Driver Non-Performance3%17%Driver Recognition 35%31%Driver Decision 43%26%Driver Performance7%19%Vehicle8%4%Environment4%3%Total (when coded to vehicle) 29,000 37,000

88%93%8%4%4%3%DriverVehicleEnvironmentCritical Reasons for Crashes Involving One Large Truck and One Passenger Vehicle Source: Large Truck Crash Causation Study, 2005

Associated Factor Traveling too Fast for ConditionsTruck Drivers in all vehicle crashes 23%Drivers in two-vehicle crashes*Large-truck drivers 15%Passenger-vehicle drivers 10% *Note: Crashes of one large truck and one passenger vehicle

Speed What Impact?Speed linked to Critical Reasons?Driver non-performanceDriver recognition errors Driver decision errors Driver performance errorsWeather conditionsRoadway typeRoadway conditions

Speeding Why?Associated-Factors linked to Speed?Type of motor carrier Pressure from motor carriers Driving experienceEmotional StateDriver in a HurryAgeUnfamiliar with RoadwayTraffic Flow Interrupted

Using LTCCS Data

Identifying ProblemsFocusing FMCSA ProgramsConducting ResearchSponsoring ResearchProviding Data to Others

Ground Breaking StudyOnly nationally representative sampleLargest number of crashesLargest number of data elements Researchers at crash sceneSound methodologyEndorsed by Congress, NHTSA

Ralph CraftPhone: (202) 366-0324Ralph.Craft@fmcsa.dot.govLTCCS Webpage:ai.fmcsa.dot.gov/ltccs/default.asp

The Large Truck Crash Causation Study (LTCCS) was conducted from April 2001 through December 2003. There were 963 fatal and injury truck crashes in the study involving 1,123 large trucks. These crashes were a representative sample of the 141,000 large trucks involved in fatal and injury crashes during the study period. Therefore, the results presented here in are all estimates of how many truck involved in fatal and injury crashes in the 33-month study period had the crash characteristics reported in the these slides. The Webster definition of cause is that when something happens, it results on something else happening, and the second happening will be the same every time. For example, if someone is hit by a large truck going 50 miles per hour, the person will die. Driving in a fatigued condition, or after consuming alcohol, or going too fast for conditions do not usually result in crashes. What they do is raise the RISK of having a crash. And what we want to find out in the LTCCS is factors that increase risk of having crashes.

So, our definition of cause if different from Websters. If we drive while we are fatigued or drunk, we will not necessarily have a crash, but that chance of having a crash increases.FARS is the National Highway Traffic Safety Administrations database of all fatal crashes.

Truck Line Express is an internet news brief published by the American Trucking Associations. The Truck Line Express numbers are based on the quotation from FARS. This is what NHTSA says about the FARS data.These are the 24 sites in 17 States where LTCCS data were collected. Each site is a city , a county, or more than one county.Data was collected on about 1,000 variables for each crash in the LTCCS.

These are the key variables coded, after data collection was completed.This is an example of a large truck crash, and how it would have been coded in the LTCCS: The SUV turns right in front of the large truck and that is the Critical Event that made the crash inevitableThe Critical Reason for the crash was driver inattention on the part of the SUV driver.Several of the Associated Factors were:The SUV driver was charged by the police as being drunkThe large truck had the green light, and the right-of-wayThe large truck was exceeding the speed limitThe large truck attempted a failed avoidance maneuver by steering to the right shoulderBoth vehicles had passengersThe crash took place in daylight, on dry pavementTheir was no distraction by other vehicles Of the estimated 141,000 large trucks involved in fatal and injury crashes during the study period, an estimated 77,000 (55%) would have been coded with the Critical Reason for the crashes in which they were involved. The estimated Critical Events are reported for those 77,000 trucks on this slide. There were 64,000 trucks that would not have been coded with the Critical Event.This slide presents the Critical Reasons that we estimate would have been coded to 77,000 large trucks involved in fatal and injury crashes during April 2001 to December 2003. This slide presents the major categories of Critical Reasons.Of the estimated 141,000 large truck involved in fatal and injury crashes during the study period, 66,000 were involved in crashes with a single passenger vehicle (passenger car, pickup truck, van, SUV). In theses crashes 44 percent (29,000) of the Critical Reasons would have been coded to the large trucks and 56 percent (37,000) of the Critical Reasons to the passenger vehicles. This slide presents the major Critical Reason categories for the two types of vehicles in these crashes.This slide shows the data from the previous slide in bar code fashion. It illustrates that for both large trucks and passenger vehicles, the overwhelming majority of Critical Reasons for crashes were coded to the drivers.Lets just look at one factor found to be important is many large truck crashes in the LTCCS Traveling too fast for conditions.Using the data from the LTCCS, we will be able to see what mistakes result from driving too fast for conditions, such as those listed.We will also be able to examine the factors that lead to driving too fast, such as those above.The LTCCS database is now on the Web, so anybody can use it. There is also a database codebook and users manual on the Web. The Web address is: www.ai.fmcsa.dot.gov/ltccs.default.asp There has never been a large truck study of this size and scope.