NMA DRL Fact Sheet ( PDF )
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One of the pervasive urban myths plaguing our highways and byways is the belief that daytime use of headlights reduces motor vehicle accidents.

It all started with a Greyhound Bus Company public relations gimmick to promote its “safety image.” There was an apparent reduction in bus accidents and the conclusion was made that the daytime headlight use must be the reason. There was a burst of publicity and daytime headlight use was christened as a great highway safety strategy.

Subsequent studies, slightly more thorough, determined that daytime headlight use on busses had no effect on accident frequency. Those studies have never received nearly as much attention.

Think about this; if you can’t see a bus during the daytime, because it doesn’t have its headlights on, there is a greater problem at play here than “visibility.”

Next, there were mandates of daytime headlight use in a few tundra-laden Scandinavian countries. Subsequent government sponsored studies proved the government was inspired in its mandating of daytime headlight use. Again, subsequent review of these favorable DRL studies indicated the high probability that factors, other than daytime headlight use, were responsible for any reduction in accident frequency.

The same scenario was subsequently repeated in Canada — the government mandates vehicles be equipped with automatic daytime running lights (DRLs) and low and behold government studies find that DRLs may be responsible for saving the human race from roadway annihilation.

Auto manufacturers, never loath to exploit a fad, climbed on the DRL bandwagon and hyped the safety benefits of irritating other drivers by shining headlights in their eyes, during daylight hours. General Motors was the most aggressive on this front.

While seldom admitted, the primary motivation for putting DRLs on American market cars is that it saves money. Rather than building one lighting system for Canada, where DRLs are mandated, and a different system for the US market, GM decided to save a few bucks by just installing the DRL equipped system on both the US and Canadian models.

One of the only large scale U.S. studies completed and published on the effects of DRLs as safety devices, was conducted by the insurance industry’s Highway Loss Data Institute. The results; vehicles equipped with DRLs were involved in more accidents than similar vehicles without DRLs. The difference was minimal, but the meaning was straight forward.

DRLs aggravate other motorists, obscure directional lights, waste fuel, “mask” other road users that don’t have headlights on, or don’t have headlights period (pedestrians and bicyclists) and their net effect on accident reduction is zero or worse. Because DRLs negatively effect other motorists, they should be omitted from all new cars by government mandate. Furthermore, all states should explore legislation that limits daytime headlight use to low beam or parking lights.

The government, in concert with various corporate interests has sold the driving public a bill of goods that doesn’t live up to its advertised claims. It seems only fair that the government and the same corporate interests undo the damage they have done.