Study Determines That Bike Lanes Result in Closer Passing

A study done in the UK determined that when drivers pass a cyclist in a bike lane they don't give as much passing distance as when the cyclist is in the road.

For the study the researchers mounted a camcorder on the rear rack of a bicycle and rode on three roads that each had sections with and without cycle lanes. On all three roads, drivers gave cyclists less room where there was a cycle lane. The greatest difference was recorded on the A6 near Garstang, Lancashire, where cars passed 18cm (7in) closer when the cyclist was in a cycle lane.

All the cycle lanes were slightly narrower than the minimum width of 1.5m (5ft) recommended by the Department for Transport.

The study, which is due to be published in the scientific journal Accident Analysis and Prevention, says that on roads without cycle lanes, drivers “consciously perform an overtaking manoeuvre”. On roads with cycle lanes, they treat the space between the centre line and the outside edge of the cycle lane as exclusively their territory and make less adjustment for cyclists.

The study concludes: “Cycle lanes do not appear to provide greater space for cyclists in all conditions.” The Highway Code tells drivers to “give cyclists at least as much room as you would when overtaking a car”

What's missing from the article (and others I could find on this) is a measure of what the resulting passing distance is or what the average difference was (they only give the largest) or how many measurements they made. But they do jump to the conclusion that this means that riding in a bike lane is more dangerous than riding on a road without one. It does look bad, but it misses an important element before determining if it's more dangerous.

That element is the standard deviation. Imagine if cars consistently pass bikes in bike lanes by 1 feet, but 50% pass a bike on the road by 2.3 feet and 50% pass by 0.5 feet.  Which road would you rather ride on (I admit this is a gross over simplification).

Nearly 100% of cars on the road are going to pass you without hitting you from behind. The problem is the outliers. The result I want to know is not which has the highest average passing distance, but rather which has the largest percentage of passes of 3 inches or less.

My hypothesis is that bike lanes keep drivers in a consistent position (on their side of the line) but passing in the road means that some drivers swing wide and some try to squeeze between you and the center line (or otherwise buzz), which is why taking the lane is so important on narrow streets. If there is a problem with bike lanes - and there very well may be - I would expect it to show up at intersections.

Comments

[Chris]

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.

[Charlie D.]

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

[chiggins]

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

[Washcycle]

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.

[Mark]

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.

[old guy]

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.

[Lee Watkins IV]

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.