 |  |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
2009 Annual Forum
View Abstract
Why Large Trucks and Passenger Vehicles Collide
Ralph Harry Craft, FMCSA, US DOT, Ralph.Craft@dot.gov
Large Trucks are involved in about 4,000 fatal, 80,000 injury, and 300,000 property-damage-only crashes every year in the United States. Sixty percent of these crashes involve a collision with a passenger vehicle – passenger car, pickup truck, van, sport utility vehicle, or motorcycle.
The Large Truck Crash Causation Study (LTCCS) examined 963 large truck fatal and injury crashes selected to be a representative sample of all truck crashes over a three year period from 2001 to 2003. The 963 crashes included 1,123 trucks and 959 other motor vehicles, and resulted in 249 fatalities and 1,654 injuries. In over half of the LTCCS crashes the first harmful event was a collision between a single truck and a single passenger vehicle.
Fatigue, drinking alcohol, and speeding are major factors in motor vehicle crashes. Although their presences does not always result in a crash, these factors, as well as other driver, vehicle, and environmental factors, can increase the risk that a crash will occur. The LTCCS defines "causation" as factors that increase the risk of crash involvement.
Data on over 1,000 elements were collected on LTCCS crashes. From this data three major variables were coded on each crash:
- Critical Event – event assigned to one vehicle that made the crash inevitable
- Critical Reason for the Critical Event – The immediate reason for the critical event which can be assigned to the driver, the vehicle, or the environment, and
- Associated Factors – All factors that were present at the time of the crash.
For all large truck-passenger vehicle crashes the passenger vehicle was coded with the critical event and critical reason in 56 percent of the crashes, and the large truck in 44 percent of the cases. In these crashes sixty percent of the critical events assigned to trucks were running out of the travel lane, failure to stop for a passenger vehicle in the truck's lane, and crossing through an intersection. Fifty percent of the critical events assigned to passenger vehicles were running out of the travel lane, failure to stop for a truck in the passenger vehicles lane, and turning left at an intersection.
When trucks were coded with the critical reason, 77 percent of the reasons were failure of the driver to recognize the pre-crash situation (inattention, distraction, etc.) or making a bad driving decision (speeding, following too close, etc.). These same two reason categories accounted for 54 percent of the reasons assigned to passenger vehicles. By contrast only 10 percent of the reasons assigned to the truck driver, but 35 percent of the reasons assigned to the passenger vehicle driver were driver non-performance (asleep, sick) or performance (overcompensation, loss of vehicle control) errors. Vehicle reasons were secondary for both classes of vehicles, but more prevalent for the large trucks.
The list of associated factors for trucks and passenger cars was similar in most cases, but trucks were coded with brake problems, unfamiliarity with the roadway, and driving under work pressure much more often that the passenger vehicles. Passenger vehicles were coded more often for making an illegal maneuver, driver fatigue, and alcohol or illegal drug use.
A critical risk analysis was undertaken to discover which factors were most likely to raise the risk of crashes for both types of vehicles. The analysis examined the relationship between the assignment of the critical reason for a crash and associated factors.
For large trucks the top 10 factors that were most likely to raise the risk of being involved in a crash included seven driver error factors (making an illegal maneuver, inadequate surveillance, traveling too fast, etc.), two vehicle factors (overweight and brake problems), and one environmental issue (stop required before the crash). For passenger vehicles the top 10 most dangerous factors in terms of assignment of the crash critical reason included six driver error factors (making an illegal maneuver, misjudgment of a gap or another vehicle's speed, inattention, etc.), and four driver condition factors (alcohol use, fatigue, illness, and illegal drug use).