Photo by Tejvan Pettinger on Flickr.

A new study in Portland finds that 94% of bicyclists stop at red lights there.

Is that just Portland? A 2012 analysis of DC cycletracks found 60% of riders stopped at red lights on the 15th Street cycletrack.

BikePortland quotes an expert who speculates that because so many people bike, it creates some peer pressure not to go through the lights.

Portland also has very short light cycles, and I wonder if that contributes. If you wait, you don’t have to wait very long. It also means that while there might be more time when nobody can go while the lights change (“intersection-clearing time”), there may be less time when one side has a green but no vehicles are actually trying to go through — the time cyclists most often go through a red light.

The DC cycletrack analysis recommended retiming the lights as one way to cut down on red light running. If cyclists leave one intersection as the light turns green, but then the next one turns red just as they arrive, they’re more likely not to wait than if it’ll only be a short wait.

This follows a general principle: the more the road system (lanes, signal timing, etc.) is designed with cyclists in mind as well as drivers, the more people will obey the markings and signals.

As another example, the study says that 4% of the Portland riders started going into the intersection before the light turned green. People often do that to get some distance from cars which might be unexpectedly turning right, or whose drivers might be looking in another direction as they start into the intersection.

DC has recently added many leading pedestrian intervals, where the pedestrian walk sign goes on before cars have a green, and also changed the law to let cyclists start going when the walk sign changes. There hasn’t been a study, but it seems very likely that far more cyclists are waiting until their legal chance to go now that the time they feel is safe, and the time when it’s legal, match more closely.

As BikePortland notes, Chicago recently announced that red light compliance rose from 31-81% when it put in dedicated bike signals, but the Portland study found they made no difference. Could the shorter light phases and/or the greater numbers of cyclists in Portland mean that people felt safer in Chicago with the signals, but already felt safe enough in Portland without?

So when someone says “we shouldn’t build more bike lanes until bicyclists follow the laws,” besides the obvious retort that 36-77% of drivers speed yet we still build roads, building the bike lane to make legal riding safe is actually one of the best ways to get bicyclists to follow those laws.

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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.