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Summary
Background
Methods
Results
Countermeasures
Tri-Level Comparison
Reference

THE RELATIVE FREQUENCY OF UNSAFE DRIVING ACTS IN SERIOUS TRAFFIC CRASHES

Background

Past research has indicated that the vast majority of traffic crashes are caused by human error. A landmark study by Indiana University (Treat, et al, 1979) found that human factors caused or contributed to 93% of the crashes investigated. In that study, anywhere from 12 to 34% of the crashes involved environmental factors (such as slick roads) while between 4 and 13% involved vehicle factors (brake failure, tire problems, etc.). The three major human factors most frequently reported in that study included:

  • Improper lookout
  • Excessive speed
  • Inattention

Other major crash studies have reported similar findings (Lohman, et al, 1978; Perchonek, 1978; Tharp, et al, 1970). While these past studies have produced very useful information, efforts to reduce the incidence of these errors have met with only limited success. The studies are also more than 20 years old and the driving environment has changed substantially.

Recently, there has been a renewed interest in problem driving behaviors such as running traffic signals, following too closely, aggressive lane changing, driving too fast for conditions, and driving while inattentive to the driving task. However, there has been a lack of specific data necessary to identify, characterize, and categorize "crash problem types," which has restricted efforts directed at problem driving behaviors. In order to develop more effective countermeasures, specific problem behaviors that cause crashes, and the conditions and situational factors associated with those crashes, must be identified.

The National Highway Traffic Safety Administration (NHTSA) commissioned a study by Veridian Engineering, Inc. to accomplish the following objectives:

    1. Determine the specific driver behaviors that lead to crashes and the situational driver and vehicle characteristics associated with these behaviors.
    2. Classify behaviorally caused crashes into "problem types" which contain common sets of characteristics.
    3. Develop a ranking of "problem types" based upon their relative frequency of occurrence.
    4. Describe potential countermeasures appropriate for each identified problem type.

The goal of this research effort was to determine the relative frequency of unsafe driving acts (UDAs) in serious crashes and then recommend countermeasures that have the potential to substantially reduce these types of crashes.