Centre/South Bike Markings Plan

Bicyclist narrowly avoids opening door -- Centre St, Jamaica Plain, Mass.
Bicyclist narrowly avoids opening door -- Centre St, Jamaica Plain, Mass.

This bicyclist had to swerve as the oblivious motorist flung open her door on Centre Street in the heart of the business district where parking turnover is high and traffic is slow.

This Thursday the City of Boston will present its proposal for bike markings on South Street and Centre St from Forest Hills to Jackson Square in Jamaica Plain. The proposal will be:

* door-zone bike lanes (DZBLs) from The Monument to Lakeview St, except for a two-block section where the width dips below 44 feet, where shared lane markings (SLMs) are proposed;

* DZBLs on the uphill side only, and on the downhill side a narrow lane with an SLM in the middle, from Hyde Square to Jackson Square and from Sedgwick Street to Jamaica Street.

* SLMs elsewhere.

The parking lane be striped at 7 feet from the curb throughout the corridor. Some additional marking to indicate the door zone may be discussed.

Most people agree that riding in the door zone is not a good idea (except when deliberately going very slowly). But some DZBL proponents argue that a) DZBLs actually move people away from parked cars, and b) you won’t get people to ride outside of the door zone.

To use their own words:

a) “First, [the additional distance between bicyclists and parked cars found in the Hampshire St. Study is] 2.4 inches further away, not 2, and that’s merely the median (average) distance   It’s clearly in the author’s conclusion that a narrowing of the spread of distances was the significant finding. Namely, that far fewer people were riding very close to the doors. And when we talk about doors and the door zone, keep in mind that when you’re on the street and a door opens, inches definitely count.”  (Pete Stidman)

b) “The problem that you are trying to solve is how to get bicyclists to ride completely outside the door zone. Without removing parking or somehow changing the dimensions of the roadway, I don’t think any type of facility and/or education will be effective in doing so.” (Charlie Denison)

I have some responses to both points:

a) The Hampshire Street study in Cambridge found that bicyclists moved away from the curb after marking a solid line at 12 feet from the curb — but they moved by an average of less than 3 inches. A San Francisco study found that shared lane markings moved bicyclists away from the door zone by an average of 8 inches. The lead author of the Hampshire Street Study has agreed with my assessment that a wheel track 11 feet from the curb, not 10 feet, is the proper cut-off for being outside the door zone 85% of the time with a 6″ margin to spare. Only 11% of bicyclists in the study were riding this far away. I am currently doing some re-analysis of the study data. One reason that few were out of the door zone is that they did the survey at rush hour, mostly approaching intersections. Traffic on Hampshire Street regularly queues up for several blocks approaching red signals in the peak period. So some of the bicyclists in the door zone may have been slowly passing cars on the right instead of being stuck in traffic for several light cycles.

b) Boston has added Shared Lane Markings in the middle of the lane in several places, and proposes to do so in the Centre-South corridor–where there is only one travel lane in each direction. These markings are supposed to direct bicyclists to ride in the middle of the lane. If it is possible to encourage people to ride in the middle of the lane, surely it is possible to encourage them to ride outside the door zone where they will impede traffic much less (at those times where traffic is moving faster than bicycle speed). A bicyclist who rides with his or her wheel at 11 feet from the curb is safely out of the door zone and in most places in the corridor is leaving 10 or more feet for a 6-foot wide passenger car to pass without changing lanes. (In fact, most drivers will crowd or cross the center line in order to provide the bicyclist with plenty of extra room when passing.)

I propose a solid white line at 10 feet from the curb with a shared lane marking completely to its left. This will provide clear guidance that bicyclists are expected to stay out of the door zone. Another San Francisco study showed that using a 9 foot parking lane instead of a 7-foot one moves the average spacing of parked cars about 4 inches further from the curb. I don’t think this a significant concern. If it is, then a solid white line could be marked at 7 feet from the curb with a series of diagonal lines (gore stripes) between the lines at 10 and 7 feet — to indicate the buffer zone to be avoided. This design would be used consistently throughout the corridor, instead of the confusing alternation between DZBL and SLM that is proposed.

To my knowledge, no city has yet tried a SLM to the left of a line indicating the door zone (as distinct from a BL with the symbol to the right of the line, or an SLM with no line).  There is an opportunity to find out how effective this configuration is in pulling people away from doors. In any case we know that SLMs, even without a line, can be more effect than DZBLs in pulling bicyclists away from the door zone.

Please come to the meeting to support shared lane markings instead of door zone bike lanes. Defend the right of bicyclists to use as much of the road as needed for safety and travel. Don’t lure bicyclists into the danger zone. The details:

Thursday, April 29th

Agassiz School cafeteria
20 Child Street, Jamaica Plain, Mass.
6 pm to 8 pm

“Bike accommodations” will be the first and major topic of the meeting.


  1. Regarding point B), I would suggest that we all study the behavior of bicyclists on northbound Harvard Ave between Brighton Ave and Cambridge St in Allston. This is where shared lane markings have been recently installed in the middle of the single travel lane, encouraging bicyclists to “take the lane”.

    I would definitely be curious to find out how many bicyclists ride in the middle of the lane outside the door zone vs how many hug the right side adjacent to the parked cars.

    Based on my observations thus far, when there are no motor vehicles waiting to pass, most bicyclists will ride in the middle, but when there are motor vehicles behind bicyclists, bicyclists tend to ride closer to the parked cars.

    I suspect that shared lane markings in the center of a travel lane are more effective when there are multiple travel lanes in that direction. In my experience, most bicyclists do not enjoy having a line of cars behind them without any way for them to pass, even when it is perfectly legal and safe for that to be the case.

    Regarding the following:
    “I propose a solid white line at 10 feet from the curb with a shared lane marking completely to its left.”

    I would recommend taking a look at Elm Street in Somerville, which is also one lane in each direction. Shared lane markings were installed there last year at 12′ (or slightly more) from the curb, with parking edge line to the immediate right of the markings. Most cyclists do not ride directly on the shared lane marking. Most ride on or to the right of the edge line. This is mainly because a motor vehicle cannot pass without crossing the center line if the bicyclist is directly on the shared lane marking. If there is oncoming traffic, passing becomes essentially impossible.

    I do agree that the law fully allows bicyclists to control the lane and prevent motorists from passing in order to guarantee their own safety. However, most bicyclists do not enjoy doing so and seem to appear to accept a slightly greater risk of dooring as opposed to an angry motorist behind them.

  2. Charlie,
    Thanks for your comments. I will check out Elm Street (and maybe stop by Wheelworks!). I’m with you until we get here: “However, most bicyclists do not enjoy doing so and seem to appear to accept a slightly greater risk of dooring as opposed to an angry motorist behind them.”

    1. As I wrote, cyclists can be outside the door zone and barely delay motorists in this corridor.
    2. This is particularly true because it is so slow and congested.
    3. When there is only one lane in each direction, cyclists should stay right when it is reasonable and safe for faster traffic to pass — but not so right as to be in the door zone.
    4. Angry motorists do not injure bicyclists (except in the rare case when the cyclist responds aggressively, and then a fistfight may well break out, or worse).
    5. Riding just a foot or two further right gives you a much (not slightly) greater risk of dooring — as opposed to an almost zero risk.
    6. Dooring is serious. There is only one study of urban car-bike collisions that I know of, and it found: “Almost all cases [of dooring] occurred on arterial roads in central areas of the city, making the Door Prize, as it has become known, the most frequently reported type of bicycle/motor-vehicle collision in central Toronto. . . . Since the injuries sustained were often more severe than average, this type of crash would appear to be a very serious concern for urban cyclists.” (The study did not give a frequency distribution of crashes for central Toronto, but found that doorings were 12% of collisions citywide.) See http://www.toronto.ca/transportation/publications/bicycle_motor-vehicle/pdf/car-bike_collision_report.pdf
    7. DZBLs reinforce and codify the misguided belief that it’s safer to be close to parked cars.

  3. I read in the JP Gazette that the City will be considering short painted lines running perpendicular to the edge of the bike lanes to warn bicyclists of the door zone. I hope they do try this. I am very interested to see if this causes bicyclists to ride in the left half of the bike lane. If it does turn out to be useful, this could be a treatment for all bike lanes or even just for areas where parking turnover is particularly high. In the latter case, it would be a good warning for bicyclists in those areas.

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