Thank you for posting your comments. The Department of Transportation has responded:

St Paul’s Pl & Caton Ave was one of the 107 locations selected in 2016 to have treatments installed as part of the Left Turn Traffic Calming program. The treatment installed here is designed to slow left turns from Northbound St Paul’s Pl to Westbound Caton Ave. The location was selected to have the treatment installed because during the 2010-2014 period there were 6 pedestrian and bicyclist injuries caused by left turning vehicles failing to yield to pedestrians on the west crossing alone.

Testing has shown the treatment to be effective at slowing left turning speeds (up to 24.4% decrease in turning speeds) as well as making the turns safer as a result of preventing vehicles from crossing over the double yellow line when turning (the rate of vehicles going over centerline when turning has dropped by 97.6%)

The Left Turn Traffic Calming Program was built on the findings of the Left Turn Study.
More information on the Left Turn Study and the Left Turn Traffic Calming program can be found at the following link: http://www.nyc.gov/html/dot/html/about/leftturnstudy.shtml