Q.1. Why was the LTCCS conducted? Don’t we already know what causes crashes?
A.1. While we know the major factors that contribute to crashes, there is no database in the nation that
focuses on the specific factors that increase the risk of crashes. In the mid-1990’s,
the Office of Motor Carriers (OMC) decided a causation study was needed to identify
specific factors that could help the agency better focus its crash prevention programs.
The study was the first of its kind in the U.S. for any type of vehicle.
Q.2. What do you mean by cause?
A.2. Cause is defined as factors that increase the risk of having a crash. Crash factors such as fatigue, speeding, consuming alcohol and drugs usually do not result in crashes. Some drivers have engaged in such behaviors while driving and not had crashes. We hypothesize that these and many other factors increase the risk of crashes, and the study is aimed at finding these factors.
The study is not aimed at finding the cause or fault in any specific crash, but finding risk factors that FMCSA, other federal agencies, and the public need to address to reduce truck crashes.
Q.3. How was the LTCCS funded and how much money was spent on it?
A.3. The Large Truck Crash Causation Study (LTCCS) was mandated by the Motor Carrier Safety Improvement Act (MCSIA) of 1999, the Act that established FMCSA as a separate administration within the Department of Transportation (DOT). MCSIA authorized $17 million for the study for the fiscal years 2000-2003. Additional funds were approved in years 2004-2006 bringing the total to about $20 million.
Q.4. How much time did the LTCCS study take and what were the major milestones?
A.4. Major milestones for the LTCCS:
- 2000 – Planning and pilot testing
- 2001-2003 - Field data collection
- 2004 - Data coding and quality checks
- 2005 - Database construction and review
- 2006 - Report to Congress
- 2006 and future years - FMCSA and the National Highway Transportation Safety
Administration (NHTSA) will conduct numerous analyses of the data, and hire contactors to undertake
Q.5. Why did it take so long to get the results?
A.5. A number of complex factors affected the length of time to conduct the study and analyze the results, as follows:
- No study of this size, complexity, and focus has ever been conducted. Previous studies of truck crash causation conducted by the National Transportation Safety Board have been limited to fewer than 400 crashes and a focus on a limited number of crash factors.
- The LTCCS collected data on 1,000 crashes with up to 1,000 variables on each crash. Each involved a large truck with a gross vehicle weight rating of more than 10,000 pounds, and resulted in at least one fatality or injury, defined as incapacitating or evident but not incapacitating.
- An attempt was made to collect data on all major crash factors the safety community thought might be responsible for crashes. The trucks and their drivers were subject to Level 1 inspections, and over 100 photographs of each crash were taken. Interviews were conducted with drivers, other vehicle occupants, and witnesses at the scene, and with motor carriers and surrogate drivers (when drivers were killed or incapacitated) away from the scene. Data was also collected from police reports, emergency medical care professionals, and other official records.
Q.6. How was the LTCCS study conducted and by whom?
A.6. FMCSA worked with NHTSA to develop a crash study plan. The goal was to investigate a nationally representative sample of at least 1,000 large truck fatal and serious injury crashes within three years. Data was collected at 24 sites in 16 States. Each site was a city, county or several counties. These sites are used by NHTSA to obtain representative samples of motor vehicle crashes.
Data collection at the sites was a two-pronged effort. One NHTSA contract researcher worked full time at each study site, except Chicago, which had two. In each site several State truck inspectors were assigned to the study. When notified of a crash, a researcher and a State truck inspector went immediately to the crash scene and recorded extensive data—sometimes as many as 1,000 data elements.
The researchers drafted a summary description of the crash based on data collected by the truck inspector and themselves, plus regular police accident reports and other official documents. The data was then sent to one of the two zone centers located in Buffalo, New York, and San Antonio, Texas, for coding.
Q.7. What are the credentials of the researchers and inspectors?
A.7. The two-person teams combined the expertise of NHTSA contract researchers who collect extensive data on over 5,000 crashes a year with the expertise of State truck inspectors who conduct over 2 million truck and truck driver inspections annually.
Q.8. What are the major elements coded for each crash?
A.8. Three major elements were coded for each crash:
Critical Event - The action or event that placed the vehicle or vehicles on a collision course such that the collision was unavoidable, given reasonable driving skills and vehicle handling. In other words, the critical event makes the crash inevitable.
Critical Reason for the Critical Event – The critical reason is the immediate reason for the critical event. The critical reason may be assigned to the driver of the vehicle given the critical event (for example, asleep at the wheel, distracted by something inside or outside the vehicle, follow too close), the vehicle (brake failure, inadequate lights), the roadway (poor design, defective signs), or weather conditions.
Associated Factors - A wide range of data was collected by field researchers and truck inspectors on a wide range of conditions present at the time of the crash, involving the drivers, vehicles, roadways, and weather. No judgment was made as to whether any factor caused the crash. In some cases data from the field was ambiguous on the presence of a particular factor. For example, examination of a truck driver’s log book, and the driver's responses to questions may provide no evidence of fatigue. However, observation of the driver at the crash scene and interviews with others may have indicated the presence of fatigue. Based on the totality of the evidence and circumstances, the researcher and coders had to judge whether fatigue was present at the time of the crash. This was not a judgment that fatigue contributed to the crash, only that the driver was fatigued before the crash.
Q.9. What are the purposes of these factors?
A.9. The list of factors serves two purposes. First, it provides additional information about the crash to describe it completely, allowing the selection of meaningful subsets of cases for analysis. Second, associated factors provide information on a broad range of factors hypothesized as being related to crash risk. For this reason, LTCCS data collection cast its net widely to identify factors.
Q.10. What approach was used to analyze the LTCCS data?
A.10. The LTCCS utilized the statistical association method which does not attempt to determine the cause of any particular crash but searches for factors that increase the risk of crashes. Objective data was collected describing the events and conditions surrounding them. In the statistical association method, cause is defined as those factors that increase crash risk. While fatigue or roadway design flaws do not always result in crashes, they do increase the risk of being involved in crashes.
Q.11. How will the data be used?
A.11. The simple tabulation of the prevalence of many variables will be very instructive. It will be used to answer such questions as:
- What is the comparative presence of alcohol, drugs, fatigue, and medical conditions among truck and other drivers involved in these crashes?
- How often are vehicle mechanical problems associated with the crashes?
- Do roadway design and adverse weather conditions show prominently in the data?
The data will allow the testing of hypotheses that certain factors are associated with increased crash risk. Most factors of interest operate through particular mechanisms, such as driving over hours-of-service (HOS) limits may lead to fatigue, which leads to inattention, which leads to failure to elect the correct speed for a curve, which leads to drifting off the road and hitting a bridge abutment.
Q.12. What is the expected outcome of the study on FMCSA’s policy making?
A.12. When fully analyzed, LTCCS data will provide a group of factors that increase the risk of large truck crashes. These factors will enable FMCSA to better focus existing crash prevention programs and to design new and more effective programs and countermeasures.
Q.13. What impact will the LTCCS have on the information DOT currently collects in its databases on highway safety?
A.13. The greatest information impact of the LTCCS may be that it is the beginning of a shift in federal highway safety databases. Currently, all major national crash databases focus on the collection of descriptive data. NHTSA, however, has begun a National Motor Vehicle Crash Causation Study (NMVCCS) that is modeled on the LTCCS. The NMVCCS study will collect crash causation data on over 1,000 crashes each year involving light vehicles—cars, pickup trucks, vans, and sports utility vehicles.