Daytime Running Lights; a popular subject. The pro's and cons of daytime running lights (DRL's) have been discussed many times. Do a search on Google and over 300000 links turn up. In Canada they have been mandatory since 1989. Many European countries have had legislation in place as far back as 1977. Till today the US of A has no laws in place that make DRL's mandatory, although all American car manufacturers utilize the module.

In my humble opinion DRL's were installed to make a motorist more visible during daytime hours. Any off you must have had the experience once when trying to pass somebody you are starting to pull out and at the same time notice a car coming in the distance. The car did not have any lights. If it had you would not even have tried to pass. One point for DRL's.

What is DRL's effect?

In-depth crash studies have shown that not having seen the other road user plays a role in 50% of the daytime crashes, and in even 80% of intersection crashes. Theoretical insight and observations explain DRL's effect mainly because of the greater contrast between vehicles and their surroundings; this increases the visibility of vehicles and makes them better identifiable. An additional effect is that vehicles with DRL are estimated to be closer than they really are.

This explains why less risk is taken while overtaking and when crossing intersections.

DRL is a way to assist road users in their visual observation task. DRL studies in the 1990s indicated reductions of 10-15% (Elvik, 1996) and 8-22% (Koornstra, 1993) in the numbers of daytime crashes in which two or more road users were involved.

 

The recent study commissioned by the EC involved a meta analysis of 41 studies of the effect for cars and 16 studies of the effect for motorcycles (Elvik et al., 2003). This showed that for cars DRL reduced the number of daytime injury crashes by 3-12%, and for motorcycles by 5-10%.

For both results we should mention that the results found per individual study (may) differ greatly. The reduction refers to daytime crashes in which more than one road user was involved. A greater effect on fatal crashes may be estimated. Some of the studies found that the DRL effect declined after some time, and others that it did not decline.

 

No proof was found that the DRL effect depends on the season. The question of how great the effect depended on latitude indeed confirmed the previous study of Koornstra et al. (1997), but the relation was less strong. The matter of the extent to which rear lights that are on in the daytime can mask the brake lights, is no longer a problem since the introduction of the third brake light (compulsory in the Netherlands since 1994). In addition, automatic switches have the option of not automatically switching the rear lights on.

The truth is, its not about seeing, but being seen! How many times have you driven in bad weather conditions, I am thinking heavy rain, snow, fog etc, and all of a sudden there is a vehicle popping up out of nowhere. It scares the living daylights out of you. If this person would have had his lights on, you wouldn't have had this 'almost heart attack', right? Two points for DRL's.

Now on the other side of the discussion, the problem with DRL's is that people forget to turn on their light switch when it gets dark or when weather conditions deteriorate and as such they are driving without taillights. This is more a driver education issue then a DRL issue. DRL's or no DRL's, people do not turn on their headlights when needed, or they turn on the parking lights. They figure as long as they can see, turning on lights is not necessary. WRONG. I quote myself: "its not about seeing, but being seen!"

Some people say the glare of the headlights will make them turn the other way. I find this hard to believe since 90% of drivers stare straight ahead while driving and do not perform the "left-center-right-center-" look around. In my years of driving I have never had a DRL bother me during daytime driving. High beams yes.

It is true that DRL's make cars who do not have them less visible, when driving behind each other. The opponents of DRL's are using this as one of the negative factors and want them banned. Then wouldn't it make more sense to have ALL cars outfitted with DRL's? Of course there is still the few people that will disconnect them.

As you see there is lots of arguments for either side. There is even an Association against DRL's. On their website they mention something about "ambient lighting" and why it does not make sense for the American continent to have DRL's. I fail to see what the amount of ambient lighting (daytime light in a day) has to do with the issue.

To finish I would like to ask this question: Why do 99% of police cars do not have their lights on in bad weather conditions?

I for one, turn on my headlights every time I get into my car because I want to be seen.

Further Research

Be Seen Day And Night