From the San Francisco Bay Guardian editorial page:

Could lowering the speed limit help us reach our biking goal by 2020?

It’s going to be hard to reach San Francisco’s official bike transportation goal, which calls for 20 percent of all vehicle trips to be taken by bicycle by 2020. Everyone in town knows that; everyone at City Hall and in the biking community agrees that some profound and radical steps would need to be taken to increase bike trips by more than 500 percent in just eight years.

It starts with safety — you’re not getting anywhere near that number of people on light, two-wheeled vehicles unless, as international bicycling advocate Gil Peñalosa recently told San Franciscans, people between the ages of eight and 80 feel safe riding on the city streets.

At the San Francisco Bicycle Coalition’s 20th Annual Golden Wheel Awards, Peñalosa — executive director of 8-80 Cities, a nonprofit that promotes creation of cycling infrastructure that is safe and inviting — laid out a prescription for designing cities around pedestrians and bicyclists (he sees riding a bike as ” just a more efficient way of walking.”) Peñalosa laid out an agenda for achieving that goal — one that includes a step San Francisco can start taking immediately: Cut vehicle speeds on all city streets to no more than 20 miles an hour.

Even if that were only done in residential areas, it would have a huge impact, and not just on bicyclists. Peñalosa cited statistics showing that only about 5 percent of pedestrians hit by cars driving 20 mph will die — but the fatality rate shoots up to 80 percent when the vehicles are traveling 40 mph.

If there are some streets where it’s impractical to have such a low speed limit, it’s imperative to have bike lanes that are separated from cars by physical barriers.

San Francisco’s Municipal Transportation Agency director, Ed Reiskin, told us after Penalosa’s speech that the notion of reducing speed limits made sense: “The logic is unquestioned that slowing speeds reduces the risk of fatality.”

But the city, it turns out, doesn’t have the power to unilaterally lower speed limits: State law requires speed limits to be set based on formulas determined by median vehicle speeds. That seems awfully old-fashioned and out of touch with modern urban transportation policy, which increasingly emphasizes bikes, pedestrians, and transit, and city officials ought to be asking the state Legislature to review those rules and give more latitude to cities that want to control traffic speed.

In the meantime, Reskin argues that a lot can be done by redesigning streets, using bulb-outs and barriers to discourage speeding. That’s fine, and part of the city’s future bike-lane policy should start with traffic-calming measures (Berkeley, to the chagrin of many nonlocal drivers, has done a great job making residential streets into bike-friendly places where cars can’t travel very fast).

Peñalosa had some other great ideas; he noted that cities such as Guadalajara, Mexico require developers to give free bikes away with each home, a program that has put 102,000 more bikes on the streets. That’s a cheap and easy concept — except that so much of the new housing in the city is so expensive, and comes with so much parking, that it’s hard to believe the millionaires who are moving into these units will be motivated by a free bicycle.

But the notion of working with Sacramento to slow down car traffic makes tremendous sense — and that ought to be one of the transportation priorities of Mayor Ed Lee’s administration.