Background 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. Rear window defoggers allow the driver to see through the rear window under adverse weather conditions. Clear vision is especially important when the driver wants to back up or change lanes.

Objectives Estimate the effectiveness of rear window defoggers in reducing crashes in which a driver is backing up, changing lanes, or performing other tasks facilitated by vision through the rear window.

Approach Statistical analysis of State crash data from the 1980's onward.

Status A draft evaluation report is circulating within the agency.