Photo by apium on Flickr.

You’re driving along in downtown DC. You get a green light and start moving, but just as you get to the next corner the light turns red. It’s frustrating! But it’s no conspiracy. There could be reasons this happens, even besides trying to help pedestrians and cyclists.

Adam Tuss’s latest NBC TV news segment brings the shocking revelation that drivers don’t like to stop at red lights, and that at least one person thinks it’s another part of the war… I mean, the nonexistent general pattern of DC deliberately pursuing policies that make things worse for drivers.

Tuss read an email on the Tenleytown listserv, by semi-anonymous poster “Paul,” alleging that DC deliberately times lights to slow down drivers. Tuss makes this the core of his story, with a response from DC transportation officials who say that this is not true, though actually, they’d really like to install a more modern signal system that makes it easier to time lights.

In the TV news tradition, Tuss also interviews a few “people on the street,” and does make sure to talk to people with multiple points of view. One driver thinks DC can probably figure out a better system, though he doesn’t say anything inflammatory. Another says it’s important to design signals to accommodate pedestrians, adding, “cities are for people, not for cars.”

At the end, Tuss and his crew take a drive on Wisconsin Avenue. We can see them leaving one intersection with a green light and getting to another one. He concludes, “Clearly, from the driver’s standpoint, some signals were not timed properly.”


Actually, no, and this is the most dangerous part of this report because it reinforces the notion that if you hit a red light, there is something wrong with the timing.

Quite simply, lights are not going to be green for everyone all the time. Wisconsin Avenue, for instance, is a 2-way street. Any timing that gives successive green lights to people driving one direction will mean more red lights the other way.

Parts of 16th Street do have “platooning,” where lights turn green in succession. This also encourages people to drive the speed limit, since if they go faster, they’ll just hit red lights each time. Some people surely think 16th’s lights are terrible because they keep hitting red lights. Others, driving the opposite way, have a legitimate beef that they timing makes things worse for them.

Downtown, there are many main streets intersecting at various angles in close proximity. There’s no way to time all of the streets for continuous greens in every direction. Should the timing encourage people to drive north on 16th or west on streets like R and U in the evening? Both have a lot of commuters traveling in conflicting directions.

One way to combat that particular problem is to close segments of streets to car traffic. When New York closed the diagonal Broadway around Times and Herald Squares, it found that traffic flowed better because the diagonal confounded signal timings on the avenues. DC could probably help everyone better traverse a place like Dupont Circle if it reduced the number of roads coming in, but that would surely spark even more “war on cars” claims even if it actually helps cars and the people inside as well as pedestrians, cyclists, and bus riders.

There are many other reasons traffic engineers might time lights in a way that appears wrong to a driver traveling a particular direction. Contributor and engineer Andrew Bossi offered many examples, such as:

Gap Provision: Providing breaks in traffic, such as to allow nearby uncontrolled interactions to operate adequately.  Without these breaks, some uncontrolled intersections may never be able to clear out, subsequently requiring some treatments such as an additional traffic signal — which would only increase motorists’ delays.  Breaks in traffic improve net mobility for the greatest amount of road users.


Still, many signals in DC aren’t timed with a lot of forethought. DC doesn’t have a state-of-the-art system

to control all of the lights centrally.

Many individual decisions get made based on local neighborhood pressure, the District Department of Transportation (DDOT)‘s James Cheeks has told me and others. That can have its pros and cons; sometimes neighbors know well where the trouble spots are, but it also makes the overall system haphazard.

Many signal timings could be better. If DDOT changes them, however, it won’t necessarily ensure that Adam Tuss always gets a green. What helps move on group of drivers could slow down another group. Also, as people say in Tuss’s story, drivers aren’t the only people on the roads.

In some places, DC could time signals to help buses get past a trouble spot when they cross a busy road. That might mean drivers on that main road more often get a red, but if the bus caries 20 people and 5 drivers have to wait a little longer, it’s a net gain. Pedestrians need time to cross, especially wide roads like Wisconsin in places with a lot of seniors like upper Northwest.

Any fixes to signals have to take everyone’s needs into account. That’ll surely make someone frustrated, creating good fodder for another Adam Tuss transportation story.

Update: Doug Noble, DDOT’s Chief Traffic Engineer from 2004-2007, notes in a comment:

DDOT’s system is not state-of-the-art, but is at least state of the practice from the late-90’s which is better than some major cities.  Most traffic signals in DC are in communication with the central system software ... The issue with the signal systems in DC is that there is typically insufficient in-house resources to update signal timing on a recurrent regular basis and it has been done through an outside contract city-wide every 4-6 years. ...

That issue is not unique to DDOT, rather it is a problem nationwide, there is money available for capital projects, but less resources available to operate and maintain the existing signals system (or even the new stuff once installed).

David Alpert is the founder of Greater Greater Washington and its board president. He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle.