Anne Matteson

Condition of Trucks and Truck Crash Involvement: Evidence from the Large Truck Crash Causation Study

This study, using the Large Truck Crash Causation Study (LTCCS), examined the relationship between the mechanical condition of heavy trucks and crash involvement. Two specific hypotheses were tested. First, trucks with defects and out-of-service (OOS) conditions were statistically more likely to be in the role of precipitating a crash than trucks with no defects or OOS conditions. Second, defects in specific systems, such as the brake system, were associated with crash roles in which those systems were primary mechanisms for avoiding the crash and physical mechanisms that link the vehicle defect with the crash role. Postcrash inspections showed that the condition of the trucks in the LTCCS was poor. Almost 55% of the vehicles had one or more mechanical violations. Almost 30% had at least one OOS condition. Of mechanical systems, violations in the brake system (36% of all) and the lighting system (19%) were the most frequent. Both driver and vehicle factors were found to contribute to crashes. A brake OOS condition increased the odds of the trucks being assigned the critical reason (a variable identifying the precipitating vehicle) by 1.8 times. Both hours of service violations and log OOS violations increased the odds by a larger amount—2.0 and 2.2 times respectively. In rear-end and cross-paths crashes, brake violations, especially violations related to adjustment, increased the odds of the trucks being the striking vehicle by 1.8 times.

Determination of Events Leading to Sport Utility Vehicle Rollover

To determine the major event pathways that result in sport utility vehicle (SUV) rollover, researchers at the University of Michigan Transportation Research Institute examined SUV rollover cases selected from the National Automotive Sampling System crashworthiness data system files for 1999 to 2001. Selected SUVs included the Ford Explorer, Jeep Cherokee, Chevrolet Blazer, Toyota 4-Runner, and GMC Jimmy for model years 1989 to 2001. Researchers coded up to six pre-rollover events, along with the stability of the vehicle (tracking or skidding) after each event. In addition, crash avoidance and recovery maneuvers were recorded, along with the rollover initiation type, location of rollover initiation, direction of roll, number of quarter turns of roll, location of roll, and surface condition at rollover initiation. Approximately 34% of SUV rollovers began with a loss of control caused by tire saturation, and about 75 % of the loss-of-control cases were on icy, wet, or snowy roads. Of the SUVs that ran off the road as the first event, 47% returned to the road before rolling over, and of these, 76% were tracking (presumed under control) before initial road departure. Between 40% and 49% of SUV rollover crashes experienced yaw instability while still on the roadway before roll. These rollovers may be addressed by electronic stability control devices if such devices can increase the control limits of the vehicle.