Of all the maneuvers drivers make, left turns are among the most difficult — and the most dangerous for pedestrians and cyclists. In order to turn ahead of oncoming traffic and escape the “back pressure” caused by cars piling behind them, drivers often accelerate quickly, cutting corners. The car’s “a-pillar” — where the frame meets the side of the windshield and the driver’s side door — creates a blind spot that can obscure people on foot or bike. And all of this happens under a time pressure, during which pedestrians also frequently have a signal permitting them to cross.

According to a new report by the NYC DOT, left turns caused about 19 percent of all pedestrian and cyclist deaths or serious injuries in New York City last year, three times higher than those caused by driver’s turning right. Drivers making left turns in the city caused over 100 deaths between 2010 and 2014.

“There’s a lot more going on in terms of your cognitive challenges when you’re making left turns,” said DOT Commissioner Polly Trottenberg at a news conference announcing the report.

The report, “Don’t Cut Corners,” also identifies factors more likely to increase the risk of left turn crashes at certain intersections. Reviewing crash reports from 2009 to 2013, the agency found they are more likely to happen when a car is turning from a minor street onto a major one, and that generally left-turn collisions are more frequent on wider streets. Pedestrians are more exposed in the longer cross walks, and drivers often turn faster, with a wider radius. They’re also more likely when cars turn from a one-way to a two-way street. As for those on foot or bike, seniors are most at risk. The median age for left-turn pedestrian and cyclist fatalities is 67, compared to a median age of 50 for all other collision types.

Based on the report’s findings and as part of the city’s Vision Zero agenda, the agency announced this week it will be implementing a number of intersection changes to reduce the risks. One hundred intersections will receive permanent plastic delineators, rubber curbs and marked guiding turn radii, with the goal of slowing down turns and eliminating cut corners. At 500 intersections, the DOT will install Leading Pedestrian Intervals, which time crossing lights so that pedestrians get at least a seven second head start before cars. In 2017, the agency will also roll out a public information campaign, which will include signs indicating turns should be taken at 5 mph. The DOT has said it will also consider restricting left turns or installing more dedicated left turn signals, and will continue to build out protected bicycle lanes.

These interventions have already been implemented at some NYC intersections, and the report indicates that they work. Left turn restrictions at 51 intersections contributed to a 41 percent reduction in left turn-caused injuries over the course of three years. Protected bike lanes reduced left turn injuries by 15 percent, and deadly or serious injuries by 53 percent. Leading Pedestrian Signals reduced injuries by 14 percent, and deadly or serious injuries by 58 percent. Over 400 were installed in 2015, and 500 more will be installed this year.