SFMTA Tries New Bike Lane Treatments to Keep Cyclists Clear of Door Zone

In a five foot standard bike lane, bicyclists really only have about one to two feet, if you consider the door zone. Animation/graphics by Carly Clark. Photo of Polk Street between O'Farrell and Geary by Bryan Goebel.

The door zone is one of the biggest urban threats to bicyclists. Conventional bike lanes that squeeze bicyclists between the door zone and automobile traffic leave little room for error, but the San Francisco Municipal Transportation Agency is piloting a series of projects designed to encourage bicyclists to steer clear of the door zone.

On sections of Polk Street, pictured above (and yes, we added the green but do hope to see green bike lanes on Polk Street some day soon!), the SFMTA has painted in a batch of T’s in the bike lanes that are supposed to guide bicyclists away from the door zone. While the treatment seems to be an improvement over typical door zone lanes, it also highlights how little street width is available for cyclists to ride safely.

I asked our graphics designer Carly Clark to do a little photoshopping to illustrate how much real space bicyclists have if you consider the door zone. If you take a standard five foot bike lane, like the one above, and factor in the door zone, you realize bicyclists are only given a sliver of a space that is about one to two feet wide, depending on the width of the lane, and the size of a car door.

According to the SFMTA, dooring is the second most common form of injury collision involving cyclists, behind unsafe speed, though the San Francisco Bicycle Coalition (SFBC) points out that dooring is the highest injury collision type caused by motorists or their passengers.

A "T" on Howard Street. Photo: SFMTA

The SFMTA has installed the T treatments on Polk between Post and Golden Gate and in the bike lanes on Howard Street between 5th and 7th. So far, according to the agency, they seem to be effective:

We’ve done before/after studies on both Polk and Howard where we were able to reduce the number of cyclists riding in the door zone. On Howard Street (study conducted 2006) the average distance from the curb where cyclists rode increased from 10.3 feet to 10.9 feet, with 24% riding in the door zone before and 10% after.  On Polk Street (study conducted 2009-10) the average distance from the curb where cyclists rode increased from 10 feet to 10.4 feet, with 41% riding in the door zone before and 30% after.

The SFMTA is also experimenting with a cross-hatch design to keep bicyclists out of the door zone on 17th Street between Dolores and Guerrero streets.

The T treatment is becoming common in more cities, and is also highlighted in the Urban Bikeway Design Guide, said David Vega-Barachowitz, the sustainable initiatives program manager for the National Association of City Transportation Officials.

Designing Better Bike Lanes

“I think that cities are really embracing the general principle that you shouldn’t put a bike lane right in the door zone,” he said.

NACTO’s recently released Urban Bikeway Design Guide encourages left-side bike lanes on one-way streets and buffered bike lanes to “provide greater shy distance between motor vehicles and bicycles.” The minimum requirements are outlined in the guide, said Vega-Barachowitz, but creating a buffer zone between moving and parked cars is what’s recommended.

When placing a bike lane next to a parking lane, the guide also encourages a 4-inch solid line between both lanes, with a 14.5-foot distance between the edge of the bike lane and the curb. A 2006 study by the SFMTA found that placing the right stripe of the bike lane farther from the curb was more effective at keeping bicyclists out of the door zone than it was at keeping cars closer to the curb.

Some cities have opted for sharrows on some streets instead of bike lanes to keep bicyclists out of the door zone, but Vega-Barachowitz noted that a bike lane has a greater calming effect on a street than just shared lane markings. A street with sharrows may also not meet the 8 to 80-year-old standard being pushed by bike advocates. More cities are now recognizing, however, that door zone bike lanes are not good engineering.

Long Beach and Salt Lake City recently began experimenting with hybrid sharrow lanes. Green paint and sharrows demarcate the space for bicyclists while improving their lateral position in a lane that is also shared with auto traffic.

“Those kinds of solutions are going to emerge in a more sophisticated way over the next five years as people use color more frequently and understand riders’ habits when they’re in consistent streams,” said Vega-Barachowitz.

The cross-hatch marks on 17th Street. Photo: Bryan Goebel


Of course, staying out of the door zone is not only about design, but about educating bicyclists “to make sure that their lateral positioning in the bike lane is outside the door zone,” said Vega-Barachowitz.

“In general, the designer should design it so that bicyclists will use it that way, but you know, in a street in Boston where there’s really not that much right of way to begin with, you’re going to have people that aren’t necessarily that comfortable riding in the road that are going to be riding in the door zone because they’re trying to move as far away from cars as possible.”

Bert Hill, a certified cycling instructor who teaches the San Francisco Bicycle Coalition’s popular Urban Cycling Workshops, advocates staying four feet away from car doors and said most students are not aware of the door zone.

“What they do understand after a little while is the biggest danger in the door zone is not hitting the door with your bike. It’s actually being on the outer edge and having your handlebar encounter the door edge,” he said. “What happens is it pulls your front wheel hard to the right and when you do that your bike frame moves to the left and so you’re almost always thrown into traffic.”

And that, according to Hill, is what has lead to many dooring fatalities.  “That’s why we advocate the full four feet, because you can be outside of the door itself, but if just the edge of your handlebar catches it, that does it.”

Hill said if he had a choice between door zone bike lanes and sharrows, he would prefer sharrows. And while he’s supportive of the SFMTA’s door zone treatments, he’s not sure that bicyclists understand what they are.

“I think it’s a really good idea where you don’t have sharrows,” said Hill. “But I think the only problem with it is that nobody understands that very well. I think it’s a good thing to know if you’re a bicyclist, but in my opinion it’s not as good as sharrows at telling motorists that the bicyclist is expected to be there.”

  • Wayne Pein

    icarus12 anonymously relied “Good point.” Which one of my many points do you think is good? 

    You seem to have faith that inexperienced and younger riders can be made safe by paint markings and that longitudinal separation is the key to safety. Would the “safe” Bike Lanes be placed by the same geniuses that placed the Door Zone Bike Lanes? 

    Bike Lanes are the “water wings” of the terrestrial world: perpetual dependency unless one is taught to not need them.

  • Icarus, taking a car to visit your dad in Marin sounds like an eminently sensible thing to do, and I would’ve made the same choice. This kind of occasional day trip to a location not easily accessible by bike or transit is what Zipcar and CityCarShare are perfect for. In the case of commuting, many, many people find Caltrain and BART preferable to driving, some even prefer Muni to driving even if they own a car. If I’m going downtown, if I don’t bike, I always choose Muni over driving because parking is expensive, annoying, and often ends up taking as long as Muni. It is definitely a choice on my part. People make choices where they live. I believe time will prove the trade-offs people made of accepting long commutes in order to obtain cheaper, larger houses will prove uneconomical. We’re already seeing a trend of people choosing smaller houses/apartments in more central locations that reduce their transit times and costs, or even eliminate their need for car ownership altogether.

    On Polk Street (in the original posting above) 77% of people who patronize it live close enough to walk. Reducing parking, traffic, and congestion might actually increase business on Polk Street among its prime customers, not hinder it in any way. It’s also a neighborhood richly served by transit and not all that difficult to bike to. Not every neighborhood needs to be a car-friendly destination, especially one as densely populated as this one, so the trade-off of parking for bike lanes seems to me a net societal benefit.

    I do hear the concern about the people with the least resources among us being pushed farther afield as commuting becomes more difficult and expensive. It may even be the case that far flung suburbs will be completely abandoned and degenerate into squatters’ ghettos for those who can scavenge a life there.  But I don’t think the answer is to defend driving private cars, as the people with the least resources will be quite quickly priced out of gasoline and car ownership altogether and will benefit the least from this advocacy. Better to do what Habitat for Humanity is doing in Daly City building 36 low income condominiums within walking distance of BART. You’re right that poor people will have the least choices and the least access to resources. However, my guess is in just a couple years we’ll see 2 or 3 poor families living in an urban apartment with no car between them rather than see them driving 60 miles to work.

    A thought-provoking resource along these lines is “Facing the New Reality: Preparing Poor America for the Hard Times Ahead.”


    I recommend the pdf of the report. I realize the scenario it paints represents a discontinuity with our current reality that is hard to fathom and harder to swallow, but it does give some very useful, concrete ideas on ways communities can adapt to the lower energy future ahead, There is a section on transportation that of course includes bicycles and transit, but also jitneys, low and medium speed rail, and water transportation.

  • Tony

    i am a big fan of the cross hatching on 17th!

  • good idea. but bikers should look out for these thing themselves.


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