From http://www.nordicgroup.us/drl /
What's bad about DRLs?
1. You lose critical traffic signaling methods. Flashing your headlights is
a) the accepted signal to a trucker that it is safe to change
b) a signal to alert drivers that have forgotten to turn on their
c) a signal at a 4-way stop or in a parking lot to let the other
driver go first
d) a signal to other vehicles that you are traveling with that you
need to stop.
2.You can't turn off your lights when
a) they are glaring into another vehicle
b) they are shining into a house at the end of a cul-de-sac or tee
c) they are shining at a pedestrian.
d) You are sitting with the engine running on the side of the
road, in someone's driveway, etc.
e) you want to be able to see outside your side windows.
3. There are places where you need to drive with only your parking lights,
i.e. drive-in movie parking lots, astronomical gatherings, military bases,
4. Drivers with DRLs often forget to turn on their low beam headlights in
rain or fog and at dusk or dawn. This is especially dangerous because the
taillights do not come on until the low beams are turned on. Many drivers
believe that in rain or fog the DRLs are sufficient and fail to turn on
their low beams to activate their tail lights. When it is dark, the lack of
dashboard lights is an indicator that the low beams and tail lights are not
on, but in daytime conditions where the low beams should be used there is no
indication that the DRLs, not the lowbeams, are on.
5. They make your bulbs wear out a little faster; not a big deal if they
really provided a safety advantage.
6. They decrease your gas mileage slightly. See:
http://www.epa.gov/otaq/cert/dearmfr/cd9402.pdf . The decrease in mileage due
to the increased load on the alternator is very small, but it is still
measurable. One one of the biggest proponents of DRLs, GM, asked for and
received permission to disconnect DRLs when doing tests for their fuel
7. They annoy other drivers. This is a biggie. "In 1998, after receiving
hundreds of complaints, NHTSA acknowledged that the intensity limits were
too high and proposed reductions in DRL intensity. NHTSA cited a study by
Kirkpatrick, et. al. (1989), that said that at 2000cd, the glare from DRLs
was rated at no worse than "just unacceptable" in 80% of the responses. At
4000cd, the glare was rated no worse than "disturbing" in 80% of the
responses. These subjective ratings are based on the DeBoer scale.
Corresponding to these ratings, they found that at 4000cd the probability
that the rearview mirror would be dimmed was about 70%. At 2000cd the
dimming probability was 40%. At 1000cd, the dimming probability dropped to
10%." The NHTSA has now proposed that the European standard for DRL
brightness be adopted. Expect the automakers to oppose this since it would
add cost to do DRLs properly.
8. The people in favor of DRLs are so dimwitted and have such weak positions
that DRLs must really be bad. Yeah, no one should be against something just
because some really stupid people are in favor of it, but doesn't it make
you uneasy to support something when someone else is supporting the same
thing based on inaccurate and misleading "data?" In California, the way the
majority of voters determine how to vote on ballot measures is by looking at
the groups and people that support and/or oppose the measure, because it's
very difficult for a layman to figure out what the ballot measure really
means when each side is claiming that it will be better for the children if
it passes or fails.
What's good about DRLs?
1. They are proven to reduce head-on collisions on two lane roads,
especially at dawn and dusk. This is what they were designed to do, and if
they were implemented just to do this then you wouldn't see much opposition
to them. You often see signs on roads in California proclaiming "Daylight
Safety Test Section -- Turn on Headlights." These are the places where DRLs
would be useful. Sadly, instead of coming up with a way to use DRLs only
when appropriate, certain parties would like them to be on all the time.
Why? Money. It's cheaper to implement a lame system than a well-designed
2. They counteract the lack of common sense of dimwitted drivers that fail
to turn on their headlights when it's foggy, rainy, or dark. Of course this
is only a positive because these drivers are not doing the proper thing and
turning on their headlights AND taillights. If the presence of DRLs causes
drivers, who would normally turn on their regular lights in these
conditions, to not turn on their regular lights, then this is a negative. A
better solution to this problem would be sensors that trigger a warning to
the driver to turn on their lights.
3. Some of the cars bought by the worst drivers come with DRLs, i.e. Saturns
and Volvos. Thus the presence of a DRL equipped vehicle is a warning to
other drivers to be careful.