1. Report No.

DOT HS 809 724

2. Government Accession No.

3. Recipient’s Catalog No.

4. Title and Subtitle

Evaluation of Rear Window Defrosting and Defogging Systems

5. Report Date

March 2004

6. Performing Organization Code

7. Author(s)

Christina Morgan

8. Performing Organization Report No.

9. Performing Organization Name and Address

Evaluation Division; Office of Planning, Evaluation and Budget
National Highway Traffic Safety Administration
Washington, DC 20590

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

Department of Transportation
National Highway Traffic Safety Administration
Washington, DC 20590

13. Type of Report and Period Covered

NHTSA Technical Report

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

Rear window defrosting and defogging systems are not required on motor vehicles by any Federal standard. Rear window defoggers became available as optional or standard equipment in most cars during the 1970's or 1980's and are popular with consumers. Today, almost all passenger cars, minivans, and sport utility vehicles have rear window defoggers, but most pickup trucks and full-size vans do not.

The analysis examined whether there were proportionately fewer backing-up and changing-lane crashes involving cars with rear-window defoggers than cars without rear-window defoggers. The database was extracted from State crash files. The analyses did not show a benefit for rear window defoggers. The main analysis found that rear window defoggers have no effect on changing lane and backing crashes in conditions when they are most likely used (when raining or snowing, during the earlier part of the morning, or during winter).

Even though the statistical analyses did not show a significant reduction in actual crashes, we would expect most drivers to like rear-window defoggers because they are quite convenient, and improved rearward vision helps a driver feel more mobile and secure when changing lanes or backing up.

17. Key Words

rear window defrosting and defogging systems; statistical analysis; evaluation; State crash files

18. Distribution Statement

19. Security Classif. (Of this report)

Unclassified

20. Security Classif. (Of this page)

Unclassified

21. No. of Pages

49

22. Price