Left Turn Safety

What is it?

Left turn safety treatments consist of installing waist-high vertical delineator posts, small rubber speed bumps, and paint to create enhanced center lane lines and painted safety zones to encourage slower, wider left turns and increase drivers’ awareness of other road users.

How does it work?

In 2019, 40% of traffic deaths in San Francisco were caused when drivers made left turns and didn’t see the person in the crosswalk, until it was too late. By adding safety treatments to intersections that encourage drivers to take left turns more slowly (5 mph is ideal) and at a 90-degree angle—as opposed to speeding through at an angle—drivers have more time to yield to people in the crosswalk. These treatments have been shown to substantially improve safety at intersections.

SFMTA’s Commitment to Left Turn Safety Treatments

In 2021, SFMTA piloted left turn safety treatments at seven high-crash intersections and paired the designs with a comprehensive Safety—It’s Your Turn education campaign. Overall, the efforts resulted in around a 17% reduction in average speed (1.7mph slower) and a 71% reduction in the likelihood of a car turning left at speeds over 15 mph. Due to these encouraging results, left turn safety treatments will become a key tool in SFMTA’s street safety improvement projects.