Bicycle Signal Priority Green Wave Project Stalled

rs_1_Kopenhagen__groene_golf_voor_fietsers.jpgGreen Wave in Copenhagen

Valencia Street is one of the most heavily biked corridors in San Francisco but its current traffic signals are timed at an auto-only capable speed of 25 mph, leaving bike riders stymied at intersections, or gasping for breath after a mad 15-block sprint. Unfortunately, most riders choose the third option of running red lights, putting not only themselves at risk of being hit, but also endangering pedestrians crossing the street.

Ideally, timing should weigh in favor of actions that have the least impact on the environment and provide the most safety for all users. Not surprisingly, this ideology has been embraced by Amsterdam, Copenhagen and Odense in Denmark. In these cities, on key bicycle corridors traffic lights have been retimed for bicycle speeds, otherwise known as a Green Wave.

Retiming traffic lights on Valencia Street to an average bicycle pace would not only preserve cyclists’ momentum and energy, it would also make the streets safer for all road users. Slowing traffic to under 14 mph exponentially decreases the severity of all crashes. Furthermore, when motor vehicle traffic is traveling at the same speeds as cyclists, it is safer for cyclists to “take the lane” when there are obstacles in bike lanes, and it may also decrease right hook crashes.

While naysayers may object that this will increase traffic congestion, it is more than reasonable to counter that real-time traffic conditions on Valencia Street have already slowed to a general range of 8 to 20 mph. It makes logical sense that retiming traffic signals for actual traffic speeds would increase traffic flow, reduce idling, and minimize stop-and-go movements, thus decreasing pollution. 


Portland, Oregon has already realized this and implemented a citywide traffic signal optimization project, which saves motorists over 1,750,000 gallons of gas and 15,460 tons of CO2 each year. It cost $533,000, which was paid for by the Climate Trust of Oregon carbon offset program. In downtown Portland nearly every street is timed for 12 mph, making these streets de facto Green Waves.

When I proposed a Green Wave on Valencia to the San Francisco Municipal Transportation Agency (SFMTA) they conducted a series of traffic models in October 2008. The results confirmed that synchronizing traffic signals for 12 mph would decrease actual travel times during peak car commute periods by as much as 3 ½ minutes.

Despite these obvious benefits for all modes of transportation, one of the nation’s most biked cities, San Francisco, has failed to move beyond simple traffic modeling. Even with recommendations from its own traffic planners, the SFMTA has insisted it does not have the funds to begin even a pilot study on Valencia Street, ignoring hard evidence of success from cities in the US and abroad.

This Streetfilm interview with cyclists on Valencia Street shows how Green Wave would benefit all street users.

Photos: zakkaliciousness on Flickr and

  • Brooke

    How much funding is actually needed to do a signal timing change on a trial basis?

  • Chris

    Awesome article, very informative. I hope the SFMTA can find the funds for this cause that would be great. Nice job on proposing it to them.

  • bc

    Having lived in Copenhagen for a year before moving back to the Bay, their incredible bike infrastructure is something I dearly miss. You’d think San Francisco would be a bit more forward thinking with its public transit and bike programs. However, Portland continues to trump us.

    One can only wish …

  • Jeffrey W. Baker

    Brooke: as the DPW amply demonstrates every year during Oracle Open World, changing signal timing is extremely easy and cheap. The only thing lacking is the executive will to act.

  • Word on getting this up and running.

  • Hilary

    How about Howard St? I find the same problem there too.

  • Tom Brown

    A green wave on Valencia would be great! I normally ride down it on quiet nights but even with no traffic cars and bikes have to stop about every 5 lights. I’m glad it isn’t timed like Fell or Oak which are not fun when there are enough cars for them to be aggressive with each other but not enough that they come to a halt.

    12mph is a nice social pace but I don’t know if a wave at that speed will do much to slow down the reckless few who seem to ignore lights. I’ve seen too many scary near accidents on Valencia but the blame goes to a mix of cars, bikes and pedestrians. 🙁

    A couple math nit-picks: “increases … speeds …. by as much as 3 ½ minutes” mixes units and

  • How can I help be part of the driving force behind getting this pilot study started? Is the bike coalition involved with this?

  • Right now we just need to do some more preliminary research, and the MTA says they don’t have the time or money. If you would like to pressure the MTA saying you would like to see this installed please do contact: the bike program bicycle(at) or call 415.701.4500
    Yes Andy from the SFBC is on board and has voiced their support.

  • Sounds great to me! 15 mph is pretty fast for a bike but mighty slow for all those impatient drivers.

  • lee

    The new light timing on Valencia between 16th and 25th (?) has been in effect now for a month or two. It creates a green wave in both directions at about 15 miles per hour.

    I have driven and riden up and down Valencia several times and I’m very pleased!

    It looks like the green wave doesn’t extend north of 15th. As a bicyclist and driver, I would love to see it extended to Market Street.