I was looking at wikipedia to find out some information about DRL regulations in UK. I know its not always a perfect source but this seems credible and was well referenced. I came across some interesting facts.

We all know that using the stock DRL system on the C5, the bulbs generate a lot of heat in the turn signal lamp units. Unless modified with DRLs this can lead to melting of the housing and water intrusion which causes the bulbs to blow regularly. I inhibited my DRLs years ago and I've never suffered from bulb failures.

When its suggested that the DRLs are inhibited, the normal reaction is that its bad to inhibit a safety feature. Studies showed that DRLs offer no statistically-significant reduction in the frequency or severity of collisions. The only areas where a reduction is seen is in Scandinavia where it is darker for a greater proportion of the day in winter.

Canada mandated DRLs. The reality is that NHTSA were against the introduction of DRLs on safety grounds because it caused ambiguity in turn signal use. It was GM that pushed to try to make cars sold in the US and Canada to the same or similar specification (ie cost). Out of interest, new regulations are being introduced in Europe for new cars but "piggy back" systems such as we have on the C5, where a light unit is dual use for turn signals and DRLs, will not be allowed.

If anyone is interested, I've copied the the extract here

Interested in any views



Shortly after Canada mandated DRLs, GM, interested in reducing the build variations of cars for the North American market, petitioned the U.S. NHTSA in 1990 to permit (but not require) US vehicles to be equipped with DRLs like those in Canada. NHTSA objected on grounds of the potential for high-intensity DRLs to create problems with glare and turn signal masking, and issued a proposed rule in 1991 that specified a maximum intensity of 2,600 cd. Industry and safety-watchdog reacted with great controversy to the proposed rule, and eventually the glare objections were set aside and most of the same types of DRLs allowed in Canada were permitted but not required effective with the 1995 model year. General Motors immediately equipped most (and, in following years, all) of its vehicles with DRLs beginning with Chevrolet Corsica and gradually introduced DRLs in the U.S. market beginning in 1995........
Public reaction to DRLs, generally neutral to positive in Canada, is decidedly mixed in the U.S. Thousands of complaints regarding glare from DRLs were lodged with the DOT shortly after DRLs were permitted on cars, and there was also concern that headlamp-based DRLs reduce the conspicuity of motorcycles, and that DRLs based on front turn signals introduce ambiguity into the turn signal system. In 1997, in response to these complaints and after measuring actual DRL intensity well above the 7,000 cd limit on vehicles in use, DOT proposed changes to the DRL specification that would have capped axial intensity at 1,500 candelas, a level nearly identical to the European 1,200 cd and identical to the initially-proposed Canadian limit. During the open comment period, a volume of public comments were received by NHTSA in support of lowering the intensity or advocating the complete elimination of DRLs from U.S. roads. Automaker sentiment generally ran along consistent lines, with European automakers experienced at complying with European DRL requirements voicing no objection to the proposal, and North American automakers vociferously repeating the same objections they raised in response to Canada's initial 1,500-cd proposal. The NHTSA proposal for DRL intensity reduction was rescinded in 2004,pending agency review and decision on a petition filed in 2001 by General Motors, seeking to have NHTSA mandate DRLs on all U.S. vehicles. The GM petition was denied by NHTSA in 2009, on grounds of severe methodological and analytical flaws in the studies and data provided by GM as evidence for a safety benefit to DRLs.In denying the petition, NHTSA said
(…)the agency remains neutral with respect to a policy regarding the inclusion of DRLs in vehicles (…) we do not find data that provides a definitive safety benefit that justifies Federal regulation (…) manufacturers should continue to make individual decisions regarding DRLs in their vehicles.

The Studies:

Numerous studies done worldwide since the 1970s have tended to conclude that daytime running lights improve safety. A 2008 study by the U.S. NHTSA analysed the effect of DRLs on frontal and side-on crashes between two vehicles and on vehicle collisions with pedestrians, cyclists, and motorcyclists. The analysis determined that DRLs offer no statistically-significant reduction in the frequency or severity of the collisions studied, except for a reduction in light trucks' and vans' involvement in two-vehicle crashes by a statistically-significant 5.7%.

 

I have noticed that in the new Audis using LED DRLs, when the turn signal is activated the DRL on that side turns off for the duration of the signal use - this must be a response to the ambiguity concern. My pet peeve (and a safety concern) is with headlight based DRLs, especially noticeable in Japanese cars, where the DRLs are bright enough that drivers forget to turn their lights on at night and drive around with no tail lamps. When you flash them they just don't get it.

 

While the study shows no significant reduction in accidents in cars using DRLs, I do tend to notice those vehicles that have DRLs on them - they just stand out a lot more than no lights at all.

 

I changed my DRLs to LED switchbacks. LEDs generate less heat per watt because they're more efficient and more energy is released as non-IR light. I'm sure this makes the point of the housing melting moot.

I prefer DRLs. I know there's many that don't like them, but I think they give the car a better look and I prefer to be seen.

 

Even though the safety improvement significance of DRLs is marginal at best, as DeeGee pointed out, I personally like the striking appearance that illuminated DRLs give to C5 Corvettes.

There's never a mistake when a C5 is approaching you on the road!

 

I totally agree - it seems that anytime I encounter a knucklehead driving at night with no headlights it's usually a Honda or a Toyota that has the high-beams on half lit as DRL's.

I know that we all hate automatic "nannies" that turn on our headlights in low light conditions, blah, blah, blah.....but watching these nincompoops navigate busy streets without headlights and taillights sure does make a compelling case for taking the simple task of turning headlights on out of the hands of the idiot behind the wheel.

Personally - I like the DRL's.