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Cyclists Often Roll Through Intersections, and That Might Be the Safer Choice

A DePaul study finds that Chicago cyclists regularly do the “Idaho stop,” a slow-rolling stop, at stop signs and even lights. And they also suggest there might be a benefit to it.

Photo: Jose M. Osorio/Chicago Tribune

The No. 1 complaint that I hear about cyclists is that they don’t stop at stop signs. Number two is that they don’t stop at stop lights. Now, thanks to DePaul’s Chaddick Institute, we have some new numbers on those habits across Chicago.

Their team staked out six intersections (three governed by lights, three by stop signs) across the city, watching 875 cyclists over 14 hours, and recording whether or not they obeyed the rules. The results were not especially surprising.

When there was no cross-traffic, cyclists came to a full stop at stop signs two percent of the time; did an “Idaho stop,” i.e. slowing down enough to yield, 43 percent of the time; and not slowing down 55 percent of the time. When there was cross-traffic, nine percent came to a full stop; 65 percent did an Idaho stop; 26 percent didn’t do either. Just two percent of cyclists not coming to a full stop at stop signs without cross-traffic will probably get all the attention because it sounds so bad, but that last one is probably the most concerning finding—26 percent of cyclists blowing stop signs with cross-traffic is a quarter of cyclists putting themselves at considerable risk.

It’s worse than driver behavior, but not as comparatively bad as you might think:

A 1968 study in Berkeley, Calif., published in Law & Society Review, found that just 14 percent of drivers brought their cars to a full stop “without being forced to do so by cross traffic” (the so-called “California roll” was the norm).

No one has more doggedly pursued the question of stop-sign compliance than John Trinkaus, who conducted an annual stopping survey at the same intersection for nine straight years in the 1970s and ’80s, finding a creeping decline. In his culminating 1997 masterwork, “Stop Sign Compliance: A Final Look,” Trinkaus revisits his old intersection and finds that the percentage of people making a full stop had dropped from 37 percent in 1979 to a mere 3 percent.

Yes: stop signs are considered by some to be the canary in the coal mine of social collapse.

In the DePaul study, compliance was better at lights, as you’d expect. When there was no cross-traffic, 30 percent did a full stop; 65 percent did Idaho stops; and just five percent barreled through the intersection. With cross-traffic present, 78 percent stopped, 17 percent made Idaho stops, and six percent did neither.

It’s not terribly surprising if you’re accustomed to navigating the city. What might be more surprising is the DePaul team’s explanation for why cyclists do this, consciously or not.

A 2007 report by Transport for London’s road safety unit found that although women make up roughly a quarter of all cyclists in that city, they are killed by large trucks at three times the rate as men (Tran, 2010). Between June and September of 2016, six cycling deaths occurred in Chicago (the average for a a full year), half of which were women struck by commercial sized trucks making turns (Sobol & Wisniewski, 2016).

We pretty well know from the data that women don’t make up half the cycling population in Chicago; the majority is male, as it is in London. So the authors are zeroing in on an interesting idea: if men are more likely to take risks on bicycles, and women are getting killed at a proportionally higher rate in these crashes, maybe there’s a benefit to taking this particular risk.

The Transport for London report posits that women are more vulnerable to truck collisions due to their tendency to be less likely to disobey red traffic signals than men. By going through a red traffic signal before it turns green, men are less likely to be caught in a truck driver’s blind spot. Instead, they get in front of the truck before it starts to enter the intersection. This research suggests that some cyclists disobey stop signs or red traffic signals in situations where their personal safety might be at risk otherwise.

The type of crash they’re avoiding is known as a right-hook crash, common enough that cyclists know the term for it. They occur when a light turns green and a cyclist going straight ends up in the blind spot of a vehicle turning right. The advice you’re usually given is to stop behind a car; that’s not always possible, so the alternative is to try to position the bike where you hope drivers will notice.

Some cities, like Chicago, have put in “bike boxes,” in order to put cyclists in front of cars where they can be seen, throwing yet more infrastructure, lines, and rules at the issue. What the DePaul study suggests is the opposite: city law should instead reflect common behavior, which seems to have some basis in common sense. (Last year, some San Francisco protesters amusingly demonstrated what happens to traffic if cyclists follow the law to the letter.) It’s what the state of Idaho has successfully been doing for decades. When some French cities tried it as a test for a similar law in Paris, it worked, too, and in Brussels.

What works best is still full, separate bike infrastructure, like on the Dearborn bike lane, which greatly increased cyclist compliance with the law. But in the absence of that, changing the law to reflect reality isn’t the danger it’s made out to be.

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