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Question about DRL's

One thing I don’t understand about DRL’s is why the tailight’s don’t come on when the DRL’s are on I know a lot of car’s if not all the headlight switch has to be turned on to have the taillight’s on. Why can’t car maker’s make a miner change in the wire’s so taillight’s come on at the same time? We have been having a lot of rainey day’s around here and most driver’ are good about turning their light’s as they are supposed to but I have noticed about 25 to 30 percent don’t have any light’s on the rear’ I can understand truck’s that are bought as cab and frame not having this feature but why car’s?

Is it a rhetorical question?

Why? => Because it’s cheap.

How to do it right? => Make use of automated controls based on ambient lighting and other factors, but it’s more expensive.


The Day time lights are mostly to make it possible to spot a vehicle coming at you the might not be easily seen in shadows or that are blending into to back ground or surrounding area. If the tail lights were on in certain conditions the brake lights coming on might not be noticeable as quick as they should be . At night the difference is much different . People have failed to turn on lights during rain for years . Same goes for the 30 minute rule before sunset .

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Do your headlights do double duty as the DRLs? Mine don’t. I’ve noticed when up against a wall that the headlight pattern changes and is much more intense when I turn the headlights on than when just the DRLs are illuminated.

None of my vechile’s have DRL’'s Ihave driven a few with DRL’s the only thing I know for sure the high beam’s would not work without the light switch being turned on.

It’s a huge problem around here. Guaranteed to see at least a half dozen vehicles on the expressway after dark with no rear lighting on. Get up alongside and their face is illuminated by the dash lighting and the road is dimly lit in front of them. These are probably the same people complaining about how lousy their headlamps are on this site :wink:


I’m getting at least 1-2 such cars spotted weekly.
I always hated DRL cheapo-band-aid for this very reason, and it was 100% predictable, yet manufacturers implemented exactly what it is.


Re my question instead of changing the wiring to have taillight’s come on change it to where dash light’s don’t come on till the light switch is turned might make better sense and would make thing’s safer.

A lot of modern cars have dash light on constantly, even when exterior lights are off, so it will not work, at least in some cases.

I was “fixing” my Subarus before by cutting one wire coming to the BCM which was disabling DRL funciton and making me to operate lights manually.

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Why do that ? Anytime you think the DRL are not enough just turn the lights on . Did you put things back before trading or selling the vehicle ?

Maybe some of this safety stuff is going to far IMHO people are getting too lazy and distracted to drive.`

I’ve actually terminated that with a switch to turn function on and off as I wished, was worried about state inspection.
Good luck to the new owner trying to figure out what that switch controls :slight_smile:

Try this:
DRL might keep someone from pulling out from a side street because your vehicle blended in with shadows.
The mandatory Back up Camera kept you from backing over a small child racing down the street on a scooter .
Adaptive Cruise might keep someone from hitting the back of your vehicle when traffic slows for no apparent reason .
The engine power being reduced automatically when brakes are applied might keep someone from driving through the front door of the local 7/11 store .

Yes , everyone should be a competent and aware driver but that is not going to happen .

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I said some not safety stuff all it seem’s to me the more the car doe’s the less attention people pay to their driving.

Some of these safety items are because people have not been paying attention to what they should for years . Or just plain doing dumb stuff.

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Agree thing’s change over the year’s I don’t know what the answer is but I think part of it is when a lot of school’s dropped driver’s ed.

We have DRLs because Canada mandated it. Really. GM decided in the 1990s to include them in all North American cars as a cost saving move, and eventually the US Government let them do it. The other manufacturers fell in line too. Canada never required rear lights as part of the deal, and here we are.

NHTSA did a study of side and from crash statistics in 2008 for collisions with other cars, motorcycles, and pedestrians and found no statistical improvement with DRLs than without.

Hey, I read it on line (Wikipedia). It must be true.

In this case, I think it is.

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Don’t know if the DRL has reduced anything . All I know is that I have noticed vehicles that I might not have noticed that had DRL . Really think it is an distinct safety feature for motorcycles .


Virtually every car sold today has automatic lights. Why is it so difficult for everyone to simply leave the light switch set to “auto”?

The manufacturer’s probablyl dont’ think there’s enough bang for the buck. The buck being the negatives of turning on the tail-lights during the daytime

  • stresses the alternator
  • causes the light bulbs to burn out sooner
  • accumulation of resistance heat can corrode or otherwise damage electrical connectors
  • reduces the amount of electrical power available for other things that need to be powered. If the battery requires recharging and there’s a only limited amount of power available, for example in stop and go traffic where the engine rpm is low, the computer will start to turn off optional stuff like the AC system, which manufacturer’s know the owner’s will complain about.