THE RELATIVE FREQUENCY OF UNSAFE DRIVING ACTS IN SERIOUS TRAFFIC CRASHES
SUMMARY OF IMPORTANT FINDINGS
This study was conducted to determine the specific driver behaviors and unsafe driving acts (UDAs) that lead to crashes, and the situational, driver and vehicle characteristics associated with these behaviors. A sample of 723 crashes involving 1284 drivers was investigated at four different sites in the country during the period from April 1, 1996 through April 30, 1997. The crashes were selected using the National Automotive Sampling System (NASS) protocol and provided a fair sample of serious crashes involving passenger vehicles in the United States. In-depth data were collected and evaluated on the condition of the vehicles, the crash scene, roadway conditions, driver behaviors and situational factors at the time of the crash. Investigators used an 11 step process to evaluate the crash, determine the primary cause of each crash, and uncover contributing factors.
Problem types in terms of crash configuration and specific behavioral errors were also identified. The following seven crash problem types, when associated with specific behavioral errors, accounted for almost half of the crashes studied where there was a driver behavioral error:
(Driver Inattention Factors) 12.9%
(Looked, Did Not See, etc.) 12.0%
(Speed, Alcohol) 10.3%
(Looked, Did Not See, etc.) 4.1%
(Inattention, Speed) 2.6%
(Following Too Closely, Speed) 1.3%
Countermeasures were identified and recommended in the following areas in order to deal with these driver behaviors and unsafe driving acts:
There were certain limitations to the data. While the sample was reasonably representative of serious crashes involving passenger cars that occurred in this country during that time period, the 723 crashes were not nationally representative because they were selected from only 4 of 24 NASS sites. Also, while the inter-rater reliability for many of the causal assessments was as high as one can expect for studies of this kind, the determination of causal factors still relied upon investigator judgment and clinical assessment.
This study confirms other research showing that driver inattention, driver impairment, unsafe vehicle speeds, and driver fatigue are important factors in serious crashes. It also provides unique insight into driver information failures and unsafe driving acts that lead to crashes under certain specified conditions.