Better red than yellow

Zweifeldig Ampel

I’ve written a lot of stupid, crazy things on this blog (I flatter myself by thinking they’re crazy, too, instead of just stupid).  But I think this entry may contain the craziest, if not the stupidest thing I’ve thought of.

It all began with a recent post on Tom Vanderbilt’s Traffic about the an FHWA study that found that marked crosswalks are less safe than unmarked crosswalks on higher speed, multi lane roads.  I don’t doubt their findings, but it’s always seemed fishy to me that in the instance of a pedestrian feature being ignored by drivers, the response is to not install them (to be fair, the report actually recommends traffic calming such as bump-outs to increase pedestrian safety). The comments to Tom’s post even mention that in countries where there is enforcement of crosswalk law, drivers yield at marked crossings, which in some cases seems to have led to routine compliance, that is, drivers actually yield to pedestrians in crosswalks without the “incentive” of getting a ticket and a big fine.

It seems like if this were a driver safety feature that was routinely ignored, it would either be regularly enforced (speed limits) or improved through engineering (left turn lanes).  Maybe I have a chip on my shoulder, but it seems like if there’s a question about a pedestrian or bicycle road feature, the response is to get rid of it (a transit road feature would not even be there in the first place), but if it’s an automobile feature, the response it to improve or mitigate it.

As I brainstormed examples, the all-red traffic signal phase – an engineering response to a safety problem caused by a road design element – floated to the top of my brain.  In this case, the road design element is the yellow light, which causes some drivers to speed up in order to not have to wait at the light.  When they judge incorrectly, and someone waiting for a green jumps the gun, the result could be described as a safety problem.

The design element that ultimately provoked this safety problem is the yellow phase of the traffic signal.  Which brings us to my crazy idea – the yellow phase may be at best unnecessary and at worst dangerous.

Presumably the yellow phase is supposed to improve safety by warning drivers that a light is about to turn red and thereby give them more time to stop before the intersection, rather than proceeding through it and risking conflict with the intersecting traffic.  This problem has been mitigated in many places by extending the length of the all-red phase, giving traffic time to clear the intersection before the intersecting traffic is allowed to proceed.  Which means that essentially the all-red phase has replaced the function of the yellow phase.

In the real world, though, the yellow phase may have another function.  We are taught that yellow means caution, so maybe the presence of a yellow light encourages drivers to stop more gradually and thereby decrease the likelihood of a rear-end crash.  On the other hand, if drivers get used to seeing an abrupt change from green to red, my guess is that they would learn to stop just as gradually as if the yellow light were still there.

It’s hard to say for sure, since they yellow phase seems to be a standard part of traffic lights worldwide.  Germany has two-phase traffic signals, but apparently they cut the green – indicating that the signal isn’t needed at all at certain times (from what I can tell, these are found at low-traffic railroad crossings).  I couldn’t find any studies of the safety benefits of yellow lights, but maybe researchers were shamed away from the topic.

Honestly, if I’m proven wrong here, I’d be relieved.  Personally I enjoy caution, and am happy that motorists get a reminder of the concept fairly regularly.  But in the interest of thinking outside the box, zero-based reasoning, and violent revolution, I thought I’d throw the idea out there.  Obviously a lunatic is not the best judge of his or her own mental state, which is why I depend on others to tell me if this idea is crazy.

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