Part I – “Critical Reasons” for Large Truck Crashes

Overview of the Study:

The Federal Motor Carrier Safety Administration (FMCSA) released the results of its  “Large Truck Crash Causation Study (LTCCS)” in July, 2007.  The study, which was conducted jointly with the National Highway Traffic Safety Administration (NHTSA), employed an exhaustive analysis of 963 of the 120,000 large truck crashes which occurred between April 2001 and December 2003 in order to explore and better identify the factors most strongly associated with serious crashes (those resulting in fatality or injury).

The study utilized detailed data collection methods, including extensive witness interviews, inspection of the trucks, review of drivers’ logbooks and other documentation, etc.   Examination of each crash involved data collection of as many as 1,000 separate elements, including:

  • the condition of the truck driver and the other drivers involved before the crash;
  • the drivers’ behavior during the crash;
  • the condition of the trucks and other vehicles;
  • roadway factors; and,
  • weather conditions.

The research data was then summarized by coding the variables for crash risk into key areas.  In this post, I will address the “Critical Reasons” identified by the study for large truck crashes.

The “Critical Reason” Conclusions:

The study defined a “critical reason” as the failure which produced the critical event (driver error, vehicle failure, etc.), and triggered the path to an unavoidable collision.  The study found large trucks to be the “critical reason” for the crash 45-55% of the time.

As applied to the drivers, the critical reason data were placed into four categories:

  1. Non- Performance: The driver fell asleep, was disabled by a heart attack or seizure, or was physically impaired for another reason;
  2. Recognition: The driver was inattentive, distracted, or failed to observe the situation adequately for some other reason;
  3. Decision:  The driver made a poor decision, such as driving too fast for conditions, followed other vehicles too closely, failed to properly judge the speed of other vehicles, etc.;
  4. Performance: The driver responded to the emergency situation in a poor manner, such as by panicking, overcompensating, exercising “poor directional control, etc.

The following table is taken directly from the study, and extrapolates the data reviewed to “the 141,000 large trucks estimated to have been involved in fatal and injury crashes during the study period. The estimates are based on a probability sample of crashes, and are rounded to the nearest 1,000 large trucks”:

Critical reasons – by major category

Estimated Numbers of Trucks in All Crashes, by Critical Reasons

Critical Reasons

Number of Trucks

Percent of Total






















Total Number of Large Trucks Coded with Critical Reason



Total Number of Large Trucks Not Coded with Critical Reason


Total Number of Large Trucks Involved in Crashes


The results of this study demonstrate that driver error was responsible for the crash in an overwhelming majority of cases.  And, standing alone, this is clearly a significant finding.  However, the study’s analysis of the “associated factors” data (covered in part 2 of this blog) sheds light into the real reasons behind these crashes — and where efforts need to be concentrated in order to make our roads safer for everyone.