If you've ridden down Valencia, 11th, or 14th, you've probably noticed that if you maintain a steady 13 mph pace you can catch all of the greens. Even if you haven't noticed, it's true. The lights are timed to let cyclists cruise right through without stopping. The "green wave" on Valencia has been in place since 2009, and the ones on 14th and 11th were added later. These bicycle green waves will soon be joined by a number of others around the city. So what's the reasoning behind the green waves other than making cycling easier?
I contacted Paul Rose of the SFMTA to see if they had any data to back up the addition of more bike lanes. He says, "The SFMTA does not have complete collision data from 2011 and 2012 yet and is unable to comment as to how the number of collisions has changed and if that can at all be related to the effects of the green wave. The agency is currently undergoing evaluation of the corridor and the green wave, however." So hopefully we'll see some data eventually. He went on to say that "Feedback on the existing green waves has been generally positive as the timing of the lights is geared to the speed of an average cyclist." Apparently feedback has been good enough that we can expect to see four new green waves next year:
• Arguello Street (from Lake to Clement streets),
• Folsom Street (from 15th to 24th streets),
• Fulton Street (from Laguna to Steiner streets), and
• North Point Street (from Stockton to Polk streets).
These should be installed by spring of next year.
Bike green waves come, like every other good cycling infrastructure development, from the Netherlands. The green wave principle, however, is widely used for automobile traffic. Main thoroughfares will often be timed to let traffic traveling roughly at the speed limit cruise through a number of lights. This doesn't just make a commute easier: it also increases the efficiency of traffic flow and decreases carbon emissions by reducing the amount of acceleration required.
While there's not a lot of hard data from San Francisco about improved safety and ridership, green waves certainly do help make it easier to commute. It requires a lot more effort to start and stop continuously than it does to just keep riding along. Apparently it will cost $117,176 to reprogram the lights and install signs.
There are some ridership numbers from Copenhagen, home of the first bike green wave. That street, the Nørrebrogade, saw an increase of 15 percent in cycling traffic, even while traffic flow was improved (currently, more than 15,000 cyclists use that green wave every rush hour). For what it's worth, about 35 percent of trips in Copenhagen are by bike.
Pedro Madruga, an Environmental Engineer at Copenhagenize Design Co., says that the green waves in Copenhagen "leave cars in second place, and thinks about cyclists. It encourages faster cyclists to go slower and it encourages slower cyclists to move a little faster. You move at the right speed. A speed where you're not endangering anyone else."
Copenhagen also used two more measures to improve the green waves: a radar sign that tells you how fast you're going, and lights on the ground that indicate whether or not you're in the green wave.
What the green wave can do is encourage safer behavior: A cyclist that generally rides faster will likely slow down to catch all the green lights (and hopefully won't run red lights), and the same can go for cars. While there isn't any rule binding a slower speed, there's incentive for everyone on the road to go the designated speed. Calmer, smoother traffic helps encourage cycling. At least in Copenhagen, there's a critical mass of cyclists, so it's easy for cyclists to feel comfortable on the roads. In San Francisco, we're still struggling with law-enforcement and drivers that aren't sure that bicycles have the right to be on the roads.
Hopefully, this relatively inexpensive and easy way to prioritize cyclists will help make the city's intentions clear. Steps like these will help people feel safe and comfortable on the roads. These are the kind of projects that will help San Francisco get even closer to the goal of 20 percent of city travel taken on bicycles by 2020. When asked whether more green waves would be in the city's future, Rose says, "At this moment, there are additional candidate locations for green wave implementations, but funds have not yet been identified." He went on to say that not every street is eligible to become a green wave because of technical reasons.
I would like to see more green waves in the city, but I have a feeling that while perceived safety might go up on a green wave street, actual safety might not -- at least not yet, with a relatively small number of cyclists on the road. But rider comfort is the best way to increase ridership, so for now, I'm all for reprogramming all of the lights.
Leif Haven is a writer and cyclist living in the Bay Area. He's can be spotted dragging himself up a hill -- literally and metaphorically.