Traffic Calming: Cities are Making Left Turns Safer with ‘Wedges’ and center-line bollards

Cities are getting smarter about using design tricks to prevent improve safety for a particularly dangerous maneuver: Left turns.

A growing number of cities are installing “slow turn wedges” and other left-turn traffic calming treatments. These treatments — typically posts placed out in the intersection — force drivers to slow down and follow the proper path while making left turns.

About a quarter of pedestrian crashes result from left-hand turns.

New York City is the leader, having installed left-turn traffic calming infrastructure in more than 200 locations in 2016 and 2017. That includes 38 “slow turn wedges” created using rubber curbs and bollards (pictured above).  These, however, can only be installed at locations between a one-way and a two-way or another one-way road.

Another tool is what New York calls a “hardened centerline” (below), where bollards prevent left-turners from crossing the centerlines to make a turn.