Effects of 24-hour headlight use on traffic safety.

Daytime running lights — generally low-wattage headlights that turn on automatically when a vehicle’s ignition is started — are a safety feature intended to reduce multiple-vehicle crashes during daylight hours by making vehicles more conspicuous to other drivers. In some countries, such as Canada, they are required to be standard equipment on all vehicles manufactured; in the United States they are permitted but not required, and were standard equipment on about 27 percent of new vehicles manufactured in 2005 (NHTSA, 2008). (Author/publisher)