1. Report No.

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

THE RELATIVE FREQUENCY OF UNSAFE DRIVING ACTS IN SERIOUS TRAFFIC CRASHES

5. Report Date

December, 1999

6. Performing Organization Code

7. Author(s) D. L. Hendricks, J. C. Fell, M. Freedman

8. Performing Organization Report No.

9. Performing Organization Name and Address

Veridian Engineering, Inc.

P.O. Box 400

Buffalo, NY 14225

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTNH22-94-C-05020

12. Sponsoring Agency Name and Address

National Highway Traffic Safety Administration

Office of Research and Traffic Records

Research and Evaluation Division

400 7^th Street, S.W., Washington, D.C. 20590

13. Type of Report and Period Covered

Summary Technical Report

1994-2000

14. Sponsoring Agency Code

15. Supplementary Notes

Paul Tremont was COTR for this study.

16. Abstract

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 from 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 provide 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.

Crash causes were attributed to either driver behavior or other causes. In 717 of the 723 crashes investigated (99%), a driver behavioral error caused or contributed to the crash. Of the 1284 drivers involved in these crashes, 732 drivers (57%) contributed in some way to the cause of their crashes. There were six causal factors associated with driver behaviors that occurred at relatively high frequencies for these drivers and accounted for most of the problem behaviors. They are: DRIVER INATTENTION - 22.7%, VEHICLE SPEED - 18.7%, ALCOHOL IMPAIRMENT - 18.2%, PERCEPTUAL ERRORS (e.g. looked, but didn't see) - 15.1%, DECISION ERRORS (e.g. turned with obstructed view) - 10.1%, and INCAPACITATION (e.g. fell asleep) - 6.4%

Problem types in terms of crash configuration and specific problem behaviors were also identified. The following seven crash problem types accounted for almost half of the crashes studied where there was a driver behavioral error: SAME DIRECTION, REAR END (Driver Inattention Factors) - 12.9%, TURN, MERGE, PATH ENCROACHMENT (Looked, Did Not See, etc.) - 12.0%, SINGLE DRIVER, ROADSIDE DEPARTURE (Speed, Alcohol) - 10.3%, INTERSECTING PATHS, STRAIGHT PATHS (Looked, Did Not See, etc.) - 4.1%, SAME TRAFFIC-WAY, OPPOSITE DIRECTION (Inattention, Speed) - 2.6%, and BACKING, OTHER, MISCELLANEOUS, ETC. (Following Too Closely, Speed) - 1.3%

A more detailed description of study methods is provided in the Final Report submitted for this effort. The final report also provides a full description of all analysis results.

17. Key Words

Unsafe driving acts, driver behavioral errors, crash problem types, causal factors, countermeasures

18. Distribution Statement

This report is available from:

National Technical Information Service

Springfield, VA 22161

(703) 605 6000

19. Security Classif. (of this report)

20. Security Classif. (of this page)

21. No. of Pages

28

22. Price