NMA Reboot: New Headlight Law is Arbitrary and Unnecessary


This weekly post features recent news stories that highlight and update themes previously covered throughout NMA E-Newsletters and Alerts.

Editor’s Note: The drivers’ paradise of Massachusetts just became the 18th state to require that drivers turn on their headlights whenever their windshield wipers are on. At best, the new law is arbitrary and unnecessary; at worst, it will create more hazardous highways. The law will also give police officers another excuse to pull over and scrutinize responsible drivers. We can think of several scenarios in which drivers would need to use their wipers sans headlights—for example, driving on a wet road after a rainstorm with sun out. Using headlights under sunny conditions has no positive impact on safety and may actually create distraction and confusion on the road, much like the Daytime Running Light issue the NMA addressed a few years back

 

Daytime Running Lights: No Statistically Significant Effect On Safety

You’re not likely to see any bold headlines, and CNN will not be interviewing Bush administration DOT officials, but the seven-year-long saga of trying to prove that Daytime Running Lights improve highway safety is coming to a close.

The official results are couched in terms like “not statistically significant,” meaning they don’t prevent crashes or make our highways safer.

The motivation for the study was a General Motors petition to make Daytime Running Lights (DRLs) mandatory on all vehicles sold in the United States. For several years prior to this GM had been fitting its vehicles with DRLs and expected the masses to respond to this patronizing gesture with their checkbooks open.

Instead, random iconoclasts and other non-believers complained about glare, blanked out directional lights, wasted fuel, and just simple irritation with the DRLs concept. They apparently went elsewhere with their checkbooks and bought cars that allowed the operator to decide when to turn the lights off and on.

Two studies preceded this last effort and they indicated some safety benefit attributable to DRLS. However, the DRL critics were just as relentless in pointing out the flaws, and bad assumptions inherent in these studies. The third effort was an attempt to address these earlier failings.

To some degree the last study was an improvement over the prior efforts, but it too failed to address many of the more difficult questions, particularly those questions that suggested DRLS not only did not improve highway safety, rather they detracted from highway safety. Fittingly, the sample population of vehicles investigated in the study were GM products.

Skipping to the final results first, the researchers could find no statistically significant evidence that DRL equipped cars and trucks were less prone to be in accidents where daytime running lights could have been a factor.

Within the study they found random blips where DRL equipped vehicles were disproportionately involved in fewer — or more — accidents than not DRL equipped vehicles. This was largely due to small sub-sample sizes where random variations will cause distortions over short time spans. When the subgroups were combined and the number of sample vehicles increased, the differences between DRL and non-DRL vehicles evaporated.

There were primary and basic assumptions made that may not be valid.

For example, the study design was based on the premise that comparing accident involvement of the two types of vehicles; those equipped with DRLs and those not equipped with DRLs would answer the “safety question.” However, the concerns raised by DRL critics are only peripherally related to actual accident involvement of DRL equipped vehicles. It was their contention that DRL equipped vehicles were causing accidents, even though these same vehicles may not have been involved in the actual accidents.

One such subset of DRL opponents consists of motorcyclists who believe DRL equipped autos and trucks diminished or confused the visibility of motorcycles that typically operate with headlights on during daylight hours. (A Japanese study that explored the effect of daytime headlight use by motorcyclists found no benefit, but that’s another topic.) The correspondingly significant increase in motorcycle accidents has added emphasis to this claim. However, the concurrent increase in motorcycle ownership and use tracks this same increase in motorcycle accidents.

Complaints of “glare,” obscured turn signals, confused distance perception (“is that one headlight close by or two headlights far away?”) and failure to use headlights during periods of low visibility were oft mentioned but not seriously explored.

Issues that were raised in the US, but given short shrift, gathered considerable momentum in some European countries. Namely, does the visual dominance of DRL equipped vehicles mask or obscure pedestrians and bicyclists? Again, the recent NHTSA study mentioned these possibilities, but did not pursue them. In all fairness this would be a difficult task. Conversely, mandating that millions upon millions of vehicles burn headlights or auxiliary lights during daylight hours is not without considerable cost.

Given the finding of “no statistically significant benefit “in this most recent study it would seem GM could better spend its time petitioning Canada to repeal its DRL mandate.

Read the full study (PDF – 2.89MB)

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3 Responses to “NMA Reboot: New Headlight Law is Arbitrary and Unnecessary”

  1. James Pappas says:

    This whole article failed to even touch on the biggest and BY FAR most dangerous aspects of the DRL issue…

    When automakers badly implement the DRL into a vehicle. And I'm looking at Ford most. Many modern vehicles have dashboards that illuminate at all times or do so independent of automatic headlights. Many of these automakers also use DRLs that are dimmed headlights. And they are far too bright.

    I can tell you I see at least a few times a week a Taurus or Escape or almost any other Ford driving with only DRLs. And do you know what that means? It means there are NO lights illuminated in the rear. ZERO. Big deal you say? A good driver will see this well ahead of time, you say? Not always so. Maybe the driver is drunk and driving along far too slowly on a highway. Maybe there are very heavy rains. Dense fog. There are absolutely certain scenarios where the best driver will find themselves in grave situations due to these DRLs.

    In Boston, you have a large number of rental cars running the highways and streets. If you don't know your car well, you'll think your lights are on when the dash is lit up like a Christmas tree and there is measurable light in front of you.

    DRLs are useless anyway. But, when badly implemented, are downright dangerous…

    • Brother John says:

      Agreed, and very well put. Stupidity like this is what we get when bad public policy meets cost-cutting in business.

      Driving is dangerous enough; turning the car into a nanny-machine encourages the driver to remain oblivious.

  2. HK Latham says:

    It's sad that there is so much opposition to DRLs. As for them being too bright, quit staring at them. The stupid driving lamps that people turn on and never think to turn off are much more of an aggravation, especially around town at night.

    I've always thought that the tail lights should be on as an added safety measure, but in our GM vehicle the full light system comes on if lighting is low. The dash lights aren't on when DLRs are on.

    It is so obvious that DLRs are beneficial. Many times it has saved us by seeing cars coming with DLRs on before I see car without them. My wife & I don't need statistics to tell me they are beneficial. We know they are. It is probably one of the best defensive driving things you can have without even thinking about it. We would turn on our lights even if they weren't automatic.

    It's just like automatically having your lights come on at dusk or poor weather conditions. It's amazing how many people don't get their lights on when they should. Recently there was even a policeman that forgot to turn his on late in the evening.

    As for the states that require lights on when wipers are on, now that is a stupid law.