I did some quick research into this subject and came up with the following
summaries of DRL studies. I have not read any of these studies in
detail so I cannot say whether they are based upon sound, scientific
principles or not. A look at the entities who performed the researches
would seem to indicate that they are.
Research Proving DRLs Are Proven Effective:
Nearly all published reports indicate DRLs reduce multiple-vehicle
daytime crashes. Evidence about DRL effects on crashes comes
from studies conducted in Scandinavia, Canada, and the United States.
A study examining the effect of Norway's DRL law from 1980 to 1990
found a 10 percent decline in daytime multiple-vehicle crashes.
A Danish study reported a 7 percent reduction in DRL-relevant crashes
in the first 15 months after DRL use was required and a 37 percent decline
in left-turn crashes. In a second study covering two years and 9 months
of Denmark's law, there was a 6 percent reduction in daytime multiple-vehicle
crashes and a 34 percent reduction in left-turn crashes. A 1994 Transport
Canada study comparing 1990 model year vehicles with DRLs to 1989 vehicles
without them found that DRLs reduced relevant daytime multiple-vehicle crashes
by 11 percent. [NOTE: the Canadian law requiring DRL came into effect in
Dec. 1, 1989].
In the United States, a 1985 Institute study determined that commercial fleet
passenger vehicles modified to operate with DRLs were involved in 7 percent
fewer daytime multiple-vehicle crashes than similar vehicles without DRLs.
A small-scale fleet study conducted in the 1960s found an 18 percent lower
daytime multiple-vehicle crash rate for DRL-equipped
vehicles. Multiple-vehicle
daytime crashes account for about half of all police-reported crashes in the
United States. A 2000 Institute study reported a 3 percent decline in
daytime multiple-vehicle crash risk in 9 U.S. states concurrent with the
introduction of DRLs. Federal researchers, using data from 4 states, concluded
that there was a 7 percent decline.
U.S. Department of Health and Human Services, Public Health Reports, Vol. 110 ;
No. 3 ; Pg. 233; ISSN: 0033-3549 (May, 1995);
Allen, J. M., Strickland, J., Ward, B., and Siegel, A.: Daytime headlights
and position
on the highway.
Am J Optometry 46: 33--36 (1969); Attwood, D. A.: Daytime running lights
project, IV:
Two-lane passing performance as a function of headlight intensity and
ambient illumination.
Technical Report RSU 76/1. Defense and Civil Institute of Environmental
Medicine,
Downsview, Ontario, Canada, 1976; Attwood, D. A.: Daytime running lights
project,
II: Vehicle detection as a function of headlight use and ambient illumination.
Technical Report RSU 75/2. Defense and Civil Institute of Environmental
Medicine,
Downsview, Ontario, Canada, 1975; Horberg, U.: Running light--twilight
conspicuity
and distance judgement. Report 215.
Department of Psychology, University of Uppsala, Sweden, 1977; Horberg, U., and
Rumar, K.: Running lights--conspicuity and glare. Report 178. Department of
Psychology,
University of Uppsala, Sweden, 1975;
Kirkpatrick, M., Baker, C. C., and Heasly, C. C.: A study of daytime
running lights
design factors. (DOT HS 807 193).
National Highway Traffic Safety Administration, Washington, DC, 1987.;
Ziedman, K.,
Burger, W., and Smith R.: Evaluation of the conspicuity of daytime running
lights.
(DOT HS 807 609). National Highway Traffic Safety Administration,
Washington, DC, 1990.
In summary, DRLs, at sufficient levels of intensity, increase visual
contrast between vehicles
and their background. Various studies have shown that DRLs can improve the
noticeability
and detectability of vehicles in the central and peripheral fields of view.
Some DRL critics attack the results of international studies on the grounds
that driving conditions
in Scandinavian countries are not comparable to North American driving
conditions. The following
studies refutes this assertion.
Cantilli, E. J.: Accident experience with parking lights as running lights.
Highway Research Record
Report No. 32. National Research Council, Transportation Research Board,
Washington, DC, 1970.
In the United States, a small-scale fleet study conducted in the 1960s
found an 18-percent lower
daytime, multiple-vehicle crash rate for DRL-equipped vehicles.
Stein, H. S.: Fleet experience with daytime running lights in the United
States. Technical Paper
851239. Society of Automotive Engineers, Warrendale, PA. 1985.
In a much larger fleet study conducted in the 1980s, more than 2,000
passenger vehicles in three
fleets were equipped with DRLs. One fleet operated in Connecticut,
another in several States in the
Southwest, and the third operated throughout the United States. A
7-percent reduction was found
in daytime multiple-vehicle crashes in the DRL-equipped vehicles compared
with control vehicles.
Aurora, H., et al.: Effectiveness of daytime running lights in Canada. TP
12298 (E). Transport Canada,
Ottawa, 1994.
In a study in Canada comparing 1990 model year vehicles (required to have
DRLs) with 1989 vehicles,
a statistically significant 11-percent reduction in daytime
multiple-vehicle crashes other than rear-end
impacts was estimated. This estimate was adjusted to take into account the
fact that about 29 percent
of 1989 vehicles were fitted with DRLs. Collisions involving pedestrians,
pedalcyclists, motorcyclists,
and heavy trucks and buses were not included in this study.
Sparks, G. A., et al.: The effects of daytime running lights on crashes
between two vehicles
in Saskatchewan: a study of a government fleet. Accid Anal. Prev 25:
619-625 (1991).
In another Canadian study, crashes of vehicles with and without DRLs in a
government fleet
in Saskatchewan were compared with a random sample of crashes involving
vehicles without DRLs.
The estimated reduction in daytime two-vehicle crashes was 15
percent. When the analysis was
limited to two-vehicle collisions most likely to be affected by
DRLs--involving vehicles approaching
from the front or side--the estimated reduction was 28 percent.
Society of Automotive Engineers Inc., Automotive Engineering Vol. 102 ; No.
8 ; Pg. 35;
ISSN: 0098-2571 (August, 1994).
In 1994 Avis, Inc. announced the results of a traveler-safety study
analyzing the incidence and degree
of damage to cars equipped with daytime running lights; the study showed a
significantly greater degree
of damage to those without daytime running lights (DRLs). Those equipped
with DRLs have their headlights
on at all times and are more visible to other drivers. During the day,
they are on at an 80% power level;
in the dark they operate at 100%. Damage severity in the non-DRL group
(measured in terms of cost)
was 69% greater than that of the DRL-equipped fleet. Only the non-DRL
vehicles experienced damage
in excess of $15,000. The Avis study involved 1500 cars with DRLs, and
1500 without, representing
approximately 29,000 rentals in eight cities in Maine, Michigan, Minnesota,
New York, Oregon, and Washington.
U.S. Department of Health and Human Services, Public Health Reports , Vol.
110 ; No. 3 ; Pg. 233;
ISSN: 0033-3549 (May, 1995).
In summary, although the studies of DRLs have differed in design, analysis
techniques, and outcome
measures, the later studies are largely in accordance with the earlier
ones, indicating that the overall
effect of DRLs on motor vehicle crashes is positive.
Another often-used anti-DRL argument is that the positive effects of DRLs
will erode over time
as the public becomes accustomed to their use on the roadways. The
following analysis proves
this argument to be not based on facts.
U.S. Department of Health and Human Services, Public Health Reports , Vol.
110 ; No. 3 ; Pg. 233;
ISSN: 0033-3549 (May, 1995).
The early and later DRL studies have shed light on concerns about the
duration of DRL effects
and the possibility of negative effects of DRLs on some road users. It has
been suggested that
when DRLs are first introduced into some part of the vehicle population,
positive crash reduction
effects will be found only because DRLs are new and unique and the vehicles
that have them
stand out from those that do not. Once people get used to seeing vehicles
with DRLs, it is conjectured,
their effects will diminish, and, if all vehicles have them, their
noticeability will be reduced or drivers
will come to ignore the extra information.
All three of the early Scandinavian studies examined the effects of DRLs
over a period of several years
when DRL use was increasing, and DRL effects were estimated in Sweden and
Finland when DRL use
was nearly 100 percent. Thus to the extent that novelty or habitation
effects occur, the effects of DRLs
in the early Scandinavian studies were still positive over time and with
close to 100 percent use.
The later studies also suggest that the initial positive effects of DRLs do
not dissipate over time.
The reductions in multiple-vehicle crashes found in the Denmark studies,
based on experience
during the first 15 months of the law and then extended to include the
first 33 months, were very similar.
This similarity led the author to conclude that the effect was a permanent
one and not due to the novelty
of DRLs. In the study in Norway, the reduction in daytime multiple-vehicle
crashes was maintained
during the 3 years in which DRLs were required for all vehicles and use was
close to 100 percent.
Effects of DRLs on Motorcycles
Another anti-DRL argument is that their use in automobiles will negate the
positive effects of motorcycles
operating with their lights on. The following studies are not as
overwhelmingly positive as for vehicles but
they do indicate that this argument has little statistical weight.
The effect of DRLs on motorcycle crashes has been studied in Denmark and
Norway, where daytime lights
were required for motorcyclists prior to the DRL law for passenger
vehicles. In the study in Norway, a
4-percent increase, not statistically significant, was found for
motorcyclist crashes. In Hansen's
evaluation of Denmark's law, daytime multiple-vehicle crashes involving
motorcycles were unchanged,
but nighttime and single-vehicle daytime motorcycle crashes decreased over
this period, leading Hansen
to conclude that there might be a "minor negative impact" of DRLs on
motorcycle crashes.
Yet another argument is whether DRLs shorten headlamp bulb life or lower
fuel economy?
Running vehicle lights in the daytime does not significantly shorten bulb
life. Systems like
those on General Motors cars that use high beams are designed to operate at
half their
normal power during daylight hours, thereby conserving energy and reducing
the effect
on a vehicle's fuel economy. NHTSA estimates that only a fraction of a
mile per gallon will
be lost, depending on the type of system used. General Motors estimates
the cost to be
about $3 per year for the average driver. Transport Canada estimates the
extra annual
fuel and bulb replacement costs to be $3-15 for systems using
reduced-intensity headlights
or other low-intensity lights and more than $40 a year for DRL systems
using regular
low-beam headlights.
Will motorists be bothered by glare? In most countries mandating DRLs,
glare has not been
an issue. However, some motorists in the United States have complained
that the systems
here are too bright. In response to these complaints, NHTSA has proposed
reducing the
maximum allowable light intensity from 7,000 to 1,500 candela, a value more
in line with
European DRLs.
There have been no studies done on the "uncool factor of DRLs" nor if
governmental
implementation of DRLs would be an infringement upon individual rights :-P
Living in Canada, I have no choice about DRLs. Now if I had a choice and I
was aware
of the above and had a say in whether DRLs would be the law of the land or
not, I would
not be against it even though I agree that DRls do not look cool :-)
Bob
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