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In my mind, there is absolutely no question whatsoever that there IS a problem with bike lanes, and it's precisely for the reason you cite, WashCycle. Instead of arguing about Ghost Bikes and building more bike lanes, the time of advocates would be much better spent educating cyclists about the dangers of being in a blind spot on a bike lane at an intersection.

I agree that predictability and ease of travel are really the benefits of bike lanes. When there are not bike lanes, some motorists give way too much room, while others give too little, as you say. With a bike lane present, there is more consistency with how much room motorists give. I would also say that motorists cross the center line less frequently when there is a bike lane present, which is probably better for their own safety.

In addition, there was a similar study by the City of Cambridge, MA that measured the position of all vehicles on the same road with and without a bike lane. It verifies what you said about standard deviation. Yes, motorists on average pass bicyclists more closely, BUT bicyclists also rode further from parked cars when bike lanes were present. The risk for dooring is usually cited being much greater than the risk of an overtaking motorist colliding with a bicyclist.

Here is a link to the Cambridge study:
http://www.cambridgema.gov/~CDD/et/bike/bike_lanes.html#hamp

My ongoing research (riding R St, between 7th and New Hampshire most weekday mornings) suggests that, were the study to have taken place in DC, they would find a helluvalot* more cars encroaching and occupying the bike lanes.

*technical term of measure

Charlie D, great point. So if a smaller average passing distance IS more dangerous - and this study doesn't show that, it would have to be balanced against the possible benefits of cyclists riding farther from parked cars.

Roadways are striped to guide vehicles and to use space more efficiently. The outcome of all of that is enhanced safety (we hope) even though it brings vehicles closer together. So if we paint a lane for bikes next to a lane for cars, no one should be surprised that they come closer than when there was no painted line.

There was a bike lane study done by TXDOT which echoes this study's findings. It went a little further, documenting that bike lanes reduced sidewalk riding, and lane divergence when drivers were passing cyclists.

I'm not sure I'd express it in terms of "standard deviation," but the issue isn't how close, it's how often there's contact.
Ie., IMHO, they're using the wrong dependent variable.

the point of striping lanes is not to increase safety, but rather to encourage the road to be used closer to capacity. without the lanes drivers will naturally provide more buffer between vehicles. What is the goal in striping bike lanes? Striped lanes DO however make drivers and cyclist FEEL safer, and feeling safer means more cyclists, and more cyclists means more overall safety than if you had less cyclist... the number of cyclists is a more powerful safety tool than the actual design of the road... at least if you get enough cyclists to pass that minimum threshold. Now, just because you are striping lanes doesn't mean you can't also provide some actual protection like say bollards, jersey barrier, parked cars, etc... which would actually make the cyclists safer in their bike lane, on top of also making it more popular.

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