“San Francisco’s Shared Lane Pavement Markings: Improving Bicycle Safety” is a study and report produced by Alta Planning + Design.


Figure 5 from the report shows bicyclists next to parked cars with doors closed. The investigators noted only that bicyclists rode a few inches further from the side of cars with the marking present. I added 2’6″ wide red doors to show that the bicyclists would have struck them.

Critique of “San Francisco’s Shared Lane Pavement Markings: Improving Bicycle Safety” HERE shows that this study is not credible research and has numerous flaws and biases.

But based on this faulty study, the Bicycle Technical Committee and the other members of the National Committee on Uniform Traffic Control Devices specified an inadequate 11’ minimum placement when next to parking for the Shared Lane Marking in the 2009 Manual on Uniform Traffic Control Devices (MUTCD). Moreover, the lateral placement Guidance for roads without parking is also flawed.

21 Responses to “San Fran’s Shared Lane Markings”

  1. Mighk Wilson Says:

    Very well done, Wayne. It’s a shame that a device with the potential to bring some remedy to door-zone bike lane tragedy has been compromised this way. I was one of those who commented to the feds on the inadequacy of that minimum distance.

  2. There’s a reason why it came out that way. I’m not happy about it, but I think it’s a mistake to say “the committee chose 11 feet.”

    First of all, the technical committee wanted to get this into the manual. Different members have their own reasons. Mine was that I wanted to provide paint-oriented advocates an alternative to bike lanes.

    Second, the technical committee doesn’t write the manual. It advises FHWA, which can do whatever it pleases (and it did, in many areas of the new MUTCD).

    Third, the technical committee reports to the full national committee, and the national committee doesn’t necessarily agree with any one of us.

    The 11-foot distance was the biggest we could get the national committee to agree on, together with language specifying greater distance could be used if engineering judgment deemed it necessary. However unsatisfactory this is, the alternative was no recommendation of this marking.

    FHWA was heavily influenced by people who don’t get the concept of where cycling safety comes from, and so it lowered the 11-foot distance from a standard to a guidance statement. Something else to be unhappy about.

    It’s amazing how many people don’t understand that avoiding dooring accidents means not riding in the door zone. The failure of people to understand that is at the root of many of these problems.

  3. Wayne Pein Says:


    Thanks for the historical clarification. It’s more accurate for me to say the Bicycle Technical Committee “accepted” 11′.


  4. John Schubert wrote: “Mine was that I wanted to provide paint-oriented advocates an alternative to bike lanes.”
    Except that it doesn’t function that way. Sharrows are almost invariably used on streets with curb lanes not wide enough (less than 23 feet) for a 12′ minimum standard bike lane (and an adjacent 11′ travel lane), which as we all know and my many FB albums show, is a door zone bike lane. So what the SLM standard encourages, is the placement of SLMs on streets with less than 23 feet of width to encourage door zone bike lane behavior, but without the stripe. So it’s not an alternative to door zone bike lanes, it a worse king of door zone guidance symbol. Even worse is the fact that SLMs are often placed in the middle of the dual hazards zone comprised of the door zone and the too-close in-lane passing zone.

    The critical failure of the committee was not tying the placement to the overall lane width, and instead having the minimum referenced ONLY to the curb. I’ve got diagrams which I plan to send to the BTC, as well as recommended improvements to the minimum standard, and guidance as a function of lane width. Should I send them through you or John C when I have them completed?

  5. Warren C. Says:

    I agree with John. Something is better than nothing. Get it in. Get feedback. Modify as necessary.

  6. @Warren – And what about the vast majority of sharrow routes with 11ft door zone placement? And your argument about something being better than nothing is a failure when applied to door zone bike lanes. They’ve been “in” as in standard, for over 30 years, and in that time have they been fixed? I think not. People are still being killed by door zone bike lanes, even though it is well known that a car doors extends through the majority of the lane. As John Schubert himself likes to say about laws and standards (and I agree with him), “First do no harm…”

  7. Warren C. Says:

    The shared lane marker lanes I have ridden in have not had this problem. There are not many in this part of the country, so my experience is not vast.

    The only serious door zone injury that I personally know of happened on a road with no markings of any type at the end of a sprint on a training ride — the cyclist’s fault for riding too close. If a shared lane marking is too close, then just don’t ride over there. It really is quite simple — a little learning can deal with this.

    John, you really are right. Dan, the shared lane marking is a big improvement over other options, so let’s get them going and make them better! Maybe a little positive thought here . . . come on, Dan!

  8. Well, I agree with both myself and with Dan. Go figgure.
    _IF_ the shared lane marking is installed in a good location — and in the not-so-wide streets Dan describes, that would be right down the middle of the travel lane — it provides a positive alternative for advocates who Must Have Paint. The shared lane markings in Bethlehem, Pennsylvania were done correctly.
    But when the shared lane marking is butchered, it’s just another use of tax dollars to endanger cyclists. Cleveland Heights is one example of that.
    The guidance statements in the MUTCD have proven to not provide protection against major flubs in shared lane marking installation.
    For that reason the technical committee is working on an installation guide. As Dan hints, John Ciccarelli is leading that effort during his copious free time.
    Dan, I know John is looking for input, and I want to see this fixed… so I say, send yer stuff to both of us. Thanks!

  9. Warren C. Says:

    Well stated, Mr. Schubert!

    Down the middle of the travel lane is best, and it is also quite simple!

  10. Thanks, Warren!
    Regarding accidents/injuries we know about:
    Bicycing tends to be amazingly safe. Bikes are skinny, maneuverable, and slow, so we have good crash avoidance ability and many of our crashes don’t result in big injury. But still, we like to reduce the crashes even farther.
    What this means is that any one person’s anecdotal evidence may inform a discussion, or it may be a data outlier.
    In the case of dooring accidents, data is just scarce enough to enable door zone bikelane advocates to deny a problem. Bike accidents that are not collisions with _moving_ motor vehicles are seldom recorded in any statistical data bank, and are often not reported at all. But when you do see dooring data, it looms large as an accident cause, and as a death cause.
    I wrote more about dooring a few months ago. Rather than repeat myself, I’ll say look at my comments on this one:

  11. Martin Pion Says:

    I found this issue and discussion of interest and would like to add some observations.
    Ferguson in North St. Louis County, Missouri, where I live has been free of any kind of bike-specific lane striping until recently when some sharrows suddenly appeared. Up to this point I had concluded that sharrows were an acceptable compromise compared to bike lane stripes, but now that I’ve seen them in practice I’ve changed my mind. They have either been located too close to the curb, or where they are in the center of the lane, they still end up putting the cyclist in the door zone.
    This once again shows the futility of trying to solve the fundamental problem of a lack of cyclist education with road paint.
    I haven’t posted yet to my blog at http://thinkbicyclingblog.wordpress.com/ on the problems I’ve just described but I hope to.
    We need a school-based program like that developed and taught in Palo Alto, Ca., middle schools to 13-year-olds in the late 1980s and early 1990s by Diana Lewiston, a protege of John Forester. The course was taught as a P.E. elective for 45 minutes every day for four successive weeks for a total of 15 hours. Ten hours was spent on-bike, much of it on roads of increasing traffic counts. At the end of the course students could use their bikes safely on most roads for transportation.

  12. Stephen Says:

    As I find out more about the SLM I think the written standards and guidance have little, if any, relevance on the street.

    The SLM markings I saw in Baltimore MD don’t follow even the 10′ standard. Most were in the door zone; one was about 4″ from a storm drain (with slots parallel to the road), and a number were under the left tires of parked cars. A MD state official mentioned some smaller towns that were surprised when contractors installed the SLM next to parked cars; they found out it was not obvious the SLM had to be in the middle of the road.

    In Delaware, some planners have spoken to a number of city employees that cycle to work, and want to put the markings in the middle of the lane, probably by consistent distance from the centerline, not the curb.

  13. Warren C. Says:

    Out here in the real world of working with governmental entities on bicycle plans, the choice is most often bike lanes or shared lane markings, with a heavy preference by many for bike lanes. We don’t have the choice of education only, Share the Road or Bicycles May Use Full Lane signs only. It is one or the other — nothing else is on the table.

    In this situation I like shared lane markings and signage as a tool in the toolbox that is an alternate to bike lanes where they make sense. If they are in the center of a lane they can work and work well.

  14. Warren – Don’t fall into the parochial trap of assuming the whole of the “real world” is the same as your part of Texas. In the real world of planning in Bethlehem, Pennsylvania, or in Hermosa Beach, CA, Sharrows were planned and installed properly. I respectfully suggest that you not assume that every planning body is just like the one(s) with which you are familiar. Instead it would have been much more intellectually honest for you to have started you comment thusly: “In my part of Texas, working with governmental entities on bicycle plans, the choice is most often bike lanes or shared lane markings, …” This way, those of us who have helped shape parts of the real world planning process to a different course than your part of Texas, will not see you as disrespectful and parochial, because you were intellectually honest in qualifying your statements.

  15. Warren C. Says:

    Dan, I think most people could figure that out for themselves. And you knew what I meant too. Please respond quickly — so you can have the last word!

  16. @Warren – Your “real world” comment came across as condescending and parochial, and yes we did figure that out for ourselves. Your preemptive strike about me having the last word is rather insecure, don’t ya think? And what does respnding quickly have to do with having the last word? Please respond, and take as long as you like to have the last word yourself!

  17. I’ve just uploaded the draft Sharrows Task Force briefing I gave to the Caltrans District 7 BAC last month. It can be seen at this public FB link. Slides 7, 8, 10 and 45-60 are the most important:


  18. Mike F Says:

    LOL @ Dan. You made my morning. In the interest of intellectual honesty, my underwear is a size 38, to fully disclose that I am a slow cyclist! Made me smile bro…

    Glad to see that you are passionate about cycling, and in the words of Rodney King and Andy D Clarke, “Can’t we all get along?”

  19. Why you should avoid the door zone:

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: