Between Atlantic Avenue and 15th Street, the road diet widened medians, shortened crossing distances, and trimmed the number of car lanes from three in each direction to two along most of the street (the northernmost blocks retained the same number of lanes). The changes were implemented using paint and flexible bollards.
After the redesign, pedestrian injuries on this stretch of Fourth Avenue fell 61 percent, total crashes dropped 20 percent, and crashes with injuries were reduced by 16 percent, according to DOT, which compared one year of post-implementation crash data to the prior three-year average [PDF]. The improvements were especially dramatic at 3rd Street, where crashes fell 41 percent, and at 9th Street, where they fell 59 percent.
DOT also tracked speeding after 9 p.m. on weekdays, with the prevalence of drivers traveling above 35 mph falling by about three-quarters, from 29 percent of southbound drivers before the road diet to just 7 percent after. (The drop in the citywide default speed limit from 30 to 25 mph took effect days after DOT finished collecting its data last year.)
Car traffic levels and travel times stayed mostly steady, with southbound evening volumes falling slightly and mixed results for northbound morning volumes. Pedestrian volumes also held steady.