Valencia Signals Re-timed to Improve Traffic Flow and Safety


As Streetsblog San Francisco reported last month, cities around the world have timed their traffic signals to favor slower moving modes, and now San Francisco has started a trial on one of the busiest bicycle routes in the city, Valencia Street.

On Thursday February 19th, the MTA re-timed six traffic signals from 16th to 21st, a pilot for a few weeks that will enable the agency to gauge the real-world impacts of reduced speeds on traffic flow.

The main goal is to improve vehicle flow and calm traffic to prevent energy intensive starting and stopping. The slower synchronized timing will also likely prove to be a great convenience to cyclists along the route.

Motorists are already seeing a benefit. Initial studies show
the re-timed signals improve overall travel time by more than a minute during peak commute hours.
Additionally, motorists will save gas and reduce pollution if they
drive at a steady 15 mph pace.

In 2002, Portland, Oregon 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, paid for by the Climate Trust of Oregon carbon offset program. The majority of streets in downtown Portland are timed at 12-15 mph for pedestrian safety and optimal traffic flow.

Untitled_2.jpgUK DOT statistics on vehicle/pedestrian collisions

In Amsterdam,
both trams and buses save time from signal re-timing. On average
trams move 1.5 minutes faster and buses 3 minutes faster.

This is expected to benefit pedestrians as well. Studies show
the severity of pedestrian
injuries in crashes with cars increases exponentially with only slight
increases in vehicle speed. Pedestrians face a 5 percent chance of
dying when hit by a vehicle traveling 20 mph, though that figure jumps
to 45 percent for a vehicle going 30
mph and 85 percent at 40 mph.

Flickr Photo: pbo31 

  • My recollection was that in 1997, when the Valencia Bike Lane was first installed, it was environmentally cleared with a mitigated negative declaration and the mitigations (LOS!) were retiming of traffic signals.

    In the absence of an ATG or VMT metric to replace LOS, one would wonder how the MTA can take this step without crossing their own current standards?


  • Greg Riessen

    The new timing plan enables a green wave of about 13 mph in both directions. For cyclists, this works well because most casual riders want to travel around that speed. It is also an appropriate speed for cars given the amount of pedestrians, double-parked trucks, etc. Best of all, the current signal timing prevents cars and bikes from speeding through the yellow/red light, which greatly improves safety for pedestrians. The new plan is a vast improvement and the MTA should be commended.

    However, in the morning on the way to work downtown, coming down the hill from 21st Street, there are many commuter cyclists that want to travel at the 18-22 mph range. This new timing plan stops them at every light. [Granted, this is better than the old plan: in order to ride the AM northbound green wave, a bike had to speed at 25 mph, zooming passed cars on the right and usually running the signals at 16th and 14th, and arriving at work in a sweat.]

    Perhaps the timing could change in the AM to benefit faster northbound commuter cyclists, and the rest of the time maintain the current, casual 13 mph progression. A different plan is less necessary in the PM because of the uphill grade, and bike traffic is not concentrated in one direction. Given the wide variety in cyclist speeds and abilities, the MTA could optimize different signalized corridors for different users at different times of the day.

    Unfortunately, car traffic has yet to figure out the reduced speed; watch the large queues of stop-and-go cars cruising at 25-30 mph, just to stop and wait at the red light. They do this on every block, and this negates any savings in fuel consumption. The MTA may want to install signage advising drivers to drive at 15 mph or take another route.

  • That’s exactly what needed, signage.

    “Signals timed for 15mph speeds’

  • MichaelSF

    Nice job, Streetsblog, for pushing the idea! This is why we’re so happy to have you in town!

  • greg

    Looks like speed limits should top out at 20mph.

  • I really enjoyed riding it today. Taking a leisurely pace from Cesar Chavez to Market, the downhill portion was almost perfect, a little bit slow. I’d catch up to the light and have 1-3 seconds before it would change. On the uphill back, the green wave pulled ahead of me by a few seconds, though I never got dropped. Again, leisurely pace–I’m sure some fixie kids would still find it too slow.

    I also noticed that motor traffic was moving quite well, though drivers weren’t racing past me to get to a red light and wait. The trip out was at 3 pm, the return at 5 pm. So evening rush hour was not negatively impacted. It will be interesting to see what the engineers at MTA have to say about it.

    thanks to them for giving this a try.

  • jdub

    Does this action indicate a new willingness at MTA to experiment with the street realm? If so, it marks a change that is most welcome and should be encouraged. This presumably was not studied endlessly, they just went out there and did it. Signage would have been nice so that drivers would know about how they might use the signals to their advantage, but this is a great step in the right direction.

    Should there be a 20mph speed limit on all SF streets? What about retiming Franklin or Fell for 20 mph as an experiment?

  • Hmm… I used to be able to catch a green at 17th and have green all the way to 14th. Now, they’re a little too slow for my taste but whatever.

  • C

    I either ride or drive Valencia every day. I appreciate bicycle timing (though I agree with Greg about it being too slow even for bikes going north.) But I fail to see how slowing cars down to 13 mph, increasing the time that they are on the road and forcing them to use a lower gear, reduces gas consumption and carbon emissions. The longer it takes cars to get where they are going, the more cars are on the road. Slowing drivers to a frustratingly slow 13 mph is only going to make them irritated and impatient, which likely makes them more dangerous. If you’re going to time Valencia for bikes, perhaps Guerrero should be timed to commute direction for cars (and parking in the left lane prohibited.)

  • Jesse

    Reading through the comments it looks like some people missed the key point that the re-timed lights are intended to make car travel *faster*, not slower. The reason for the paradox: during times of heavy (car) traffic, average car speed is slower, and by matching the “green wave” to that slower speed, cars can avoid wasting time sitting stopped at lights. Yes, it slows things down a little during times of light traffic, when cars could successfully ride a 25mph green wave the whole way down, but hopefully the gains during congestion should be enough to make it worth it for cars.

    As a bike commuter, I agree that 13mph is a little slower than I like for my morning northbound commute. But now that I know the lights are re-timed, I won’t have to race down Valencia to keep up with the wave, and that’s fine by me. I used to make it from 22nd to 16th without hitting a light, but this morning I made it all the way to 14th.

    I think they re-timed some other streets recently too. Dolores at 23rd had previously been de-synched, apparently to keep cars from racing through after coming down the hill from 24th, but they seem to have re-synched it yesterday. And while I don’t know for certain after only one day, 14th st seems to have had better light timing as well.


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