San Francisco to Study Lowering Speed Limit to 20 mph

With growing concern about pedestrian safety in San Francisco, and the city getting on board with a plan to end all traffic deaths within 10 years, Supervisor Eric Mar wants to study lowering speed limits to 20 mph, especially on streets with high collision rates.

"My hope is that as our Vision Zero process for San Francisco moves forward with engineering, enforcement and education, that we also look at policy changes like lowering speed limits, to save lives and make our streets safer," said Mar.

Vision Zero is a plan to eliminate all traffic fatalities by 2024. Under the plan, the San Francisco Municipal Transportation Agency has identified the most troubling intersections and plans to undertake quick "cost-effective" measures to improve pedestrian safety.

Mar has asked the city's budget and legislative analyst to look at three things: what the city can learn from London, New York and Paris, which have implemented 20 mph speed zones, how many lives could be saved, and the financial and environmental impacts of lowering speed limits.

London's 20 mph speed zones have led to a steady decline in injuries and deaths, especially among children, according to one study. London's program helped inspire San Francisco's 15 mph school zones.

Many San Francisco streets have default speed limits of 25 mph, including those arterial streets that pedestrian advocates say by design act as auto speedways and pose the biggest pedestrian threat. Drivers often ignore the posted speed limits, and can travel upwards of 40 mph.

But there's a life saving difference between 40 and 20 mph. A pedestrian is more likely to survive a collision with a car when the vehicle is traveling at 20 mph or under, says Nicole Schneider, executive director of Walk San Francisco.

"You can compare it to falling off a five-story building versus a one-story building," Schneider said. "At 40 mph, you have a five percent chance of living. But at 20 mph you have an 85 percent chance of living."

Some streets that could be targeted for speed reductions are in dense neighborhoods with high pedestrian injuries and fatalities, such as SoMa and the Tenderloin. Pedestrian advocates say safer designs and traffic calming measures on dangerous streets would need to go hand in hand with speed reductions.

SFMTA staffers found that 60 percent of pedestrian injuries and deaths occur on just 6 percent of streets. More than 100 pedestrians are “severely injured or killed” each year, and 800 are injured, they found.

"Reducing speeds in San Francisco is critical for the health and well-being of our community," Schneider said.

Mar hopes to propose some policy changes once the data starts coming in in the early fall.