Daytime Running Lights, DRL, Effective or Not?

I'll start with the fuel economy hit.
DRLs in Canada run at reduced intensity if it's the headlamp. If they use the "turn signals" (yellow) they will be in the 30W each area. No other lamps are on except the two DRLs. So reduced headlamps would probably draw in the area of 30-40W each and "turn signals" would be in the 30W each area. We are talking of a maximum of 80W here. That's about 1/10 of a HP. -I- can't measure the fuel economy hit of that. Perhaps -someone- can!

The Canadian Govt. "measure" of safety improvement is suspect in my eyes. How can you tell if 11% is caused by DRLs? There is a greater variation year to year in collisions. But they had to justify their actions. I have to include this negative attitude to "keep real". Perhaps they corrected for the errors I suspect, perhaps they didn't.

I do know that 70% or more drivers on the road don't really either -know- what they are doing or -pay attention- to what they are doing. Headlamps tend to grab their attention.

I also know from experience, that in certain situations on the highway, you will see a vehicle much sooner and easier if they have DRLs than if not. I am hoping this means seeing them easier means you will not pull out in front of them.

I have -NEVER- been "masked" re seeing turn signals with headlamps on. True DRLs as implemented in Canada would "mask" turn signals even less.

But appearantly there are strong opinions on this subject, so I suspect -my- experiences won't sway anyones thoughts.

 

The early studies that showed improved safety with DRLs came from Scandinavia, where the high latitude produces extended periods of low light levels. Follow-up studies at lower latitudes have been inconclusive, or mixed in results.

The issue comes down to contrast. When viewed against a dark background, lights are unquestionably helpful. Against a bright background they may work against improved visibility. A good example of this was in WWII, where sub hunting aircraft were fitted with leading edge lights on the wings. The lights made the aircraft brighter, making them virtually invisible against the daytime sky.

Another factor is differentiation. If yours is the only car with DRLs, it will be unique and stand out against the sea or other cars. If every car has DRLs, yours will be part of the background noise. This is why emergency vehicles use flashing lights, but we don't put them on every car.

Do DRLs work? From a scientific standpoint, the jury is still out. The data are starting to lean toward yes, but I find it too early to say that with certainty. From a gut feeling standpoint, they seem like a good idea.

Tom

 

This thread title is misleading. I didn't say anything about DRL's in my original post that certain parties aggressively went off topic with. Instead it addressed the mpg hit from running normal headlights in normal daylight hours.

As for DRL's, no they should not use as much energy as the normal headlamps. But that isn't what I was talking about in the original post.

Contrast is indeed the key, which is why I see no benefit to headlamps or DRL's during good daylight conditions. If someone wants to run them, fine with me. I don't oppose DRL's, but I did have to disable those on my Tundra because there are certain times when I cannot have them on...and there was no fuse or switch to turn them off unfortunately.

 

Shawn, sorry if you feel this thread was directed at you. My response was not.
With experience in Canada, we have learned that you can disable the DRLs by applying the e-brake just enough to trip the switch on it. I do that when entering and leaving amateur astronomy observing sites. The brakes don't drag enough to notice at that setting.

With the Prius, you must set the e-brake before you start the car to have the DRLs disabled. So it's obviously electronic, unlike other cars I have owned/driven.

 

There is a road that I've been using lately where headlights are really useful. It really should be a 6 lane freeway, but instead it's a curvy narrow 4 lane road (highway 17 between San Jose and Santa Cruz in California). It's kept that way because the Santa Cruz area residents are afraid that they will just be a bedroom community for Silicon Valley if the road is improved.

Travel is typically at 45-55 mph, which is about 10-15 mpg higher than I find comfortable. There are trucks going 20 mph in the right lane, which you discover typically around a blind curve. So if you want to avoid the trucks, you end up in the slot car lane at 50+ mph. I don't know what the police enforce, but I have noticed a pack of cars doing 60 past a patrol car in a 50 zone.

Headlights ON help other drivers notice your presence and distance. I think it cuts down on other cars cutting into your lane too close. And it helps drivers entering from side roads to judge your distance.

I use my headlights selectively. On freeways and around town, they don't seem to provide any assistance. On high speed, curvy, mountain roads, I think they are useful.

 

I totally agree with you !!! So little energy used for such a BIG improvement in visibility.

I have ABSOLUTELY no doubt that I can see cars coming from farther away when they have there lights on. So, if you can see them in advance you can react much more sooner in case something happens.

I think it's a good thing even if it only saves one more life !!

 

This argument could lead to a lot of changes on all sorts of levels. How about a 45 mph speed limit? That would save a lot more lives than headlights. Not just from reduced accidents either. Could well prevent some future wars over natural resources.

 

I would prefer to have DRL for my '08 Prius, but I can live without it.

 

Then let's do it, although 55 might be a better compromise.

 

Maybe (and my english is not that good sorry).

But once again this morning at 7am when it was still dark... let me tell you that the pre-90s GMC truck I saw was almost invisible among all the other cars. In fact, I saw it a bit late and it could have caused and accident.

You may argue that I could look better but all cars with DRL where highly visible.

 

Headlights when it is dark, not DRLs. I don't think anyone could deny that headlights help at night.

Tom

 

Those of you who oppose daytime lights miss the point. Up here in the frozen north, it started with buses. Then evidence came from Scandinavia that they reduced accidents at all times of day. It's not the absolute amount of light, it's the contrast that makes cars, buses,and trucks more visible to both other drivers and pedestrians. Now they are required in Canada and for good reason.
If you think that the energy used reduces your MPG, then you better not use your radio either. The fact is that the difference in mileage is not measurable.

 

According to what my Scanguage tells me, I would have to disagree with you on both of the above comments. When I monitor the current draw from the HV pack, I see no difference with the radio on or off; the reading is 1.0 amps of draw. I realize this doesn't mean the radio is a freebie but that it is under the .1 amp threshold and isn't readily measurable by the SG. When I turn on the headlights, the draw goes up to 1.6 amps. I calculate that as a 60% increase in power usage and, since that power will be ultimately replenished by the gasoline in the tank, I would say that this a very measurable difference. I should also note that my headlights are the HID version so I suspect that the difference would be even greater with regular headlights.

 

It is folks like you who have missed the point. The contrast you speak of is not noticeable at all in normal daylight. That's the problem with your argument. Nobody is denying the effect in reduced lighting conditions. There are a number of us who don't buy into wasting energy when it is not needed.

Read diamondlarry's post. Unlike you he didn't guess. He measured (while I calculated.) Ditto on what he said about the radio. Unless you are cranking it with lots of bass the mpg loss is going to be negligible.