Evaluation of Rear Window Defrosting and Defogging Systems;Technical rept

摘要

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.