Left-turn calming slows turning speeds and improves left turning drivers’ view of the crosswalk at intersections. This can result in fewer or less severe pedestrian crashes.
Portland crash data show that 20% of pedestrian crashes result from left-turning drivers failing to yield to pedestrians in the crosswalk at signalized intersections.
Results from Portland, along with New York City and the Insurance Institute for Highway Safety, indicate that left-turn calming improves pedestrian safety. Following a one-year evaluation, in 2020 we began using left-turn calming as a routine tool where recommended by our engineers.
Our pilot project evaluation is summarized below, with the full report available at the link.
How to use left-turn calming
Left-turn calming makes turns tighter, especially when two drivers are making left turns across from each other. Our evaluation has not found any risk to drivers as a result of this change.
If you need to, it is OK to drive over the small rubber bumps. They are designed to handle the load and it should not result in damage to vehicles.
If you have questions or concerns, please contact us.
Key results of the pilot project
- Left-turn calming consistently reduces turning speeds by modest but potentially significant amounts (median speed reduction of 13 percent, from an average median speed of 14.0 to 12.1 mph, across all locations).
- All left-turn calming installations nearly eliminate sharp turns in which drivers cross the centerline (reductions ranging from 82 to 100 percent).
- Hardened centerlines using rubber speed bumps are about equally effective at slowing turning speeds as hardened centerlines with flexible posts (12 percent average reduction in median speeds with bumps compared to 13 percent reduction with delineators).