Intelligent Speed Assistance: an on-road evaluation

Although approximately 29% of traffic fatalities involve excessive speed, individual vehicle technology that can reduce speeding has not been widely studied or implemented in the United States (U.S). Starting in 2022, NYC DCAS conducted the largest public pilot of active Intelligent Speed Assistance (ISA) in the U.S., with approximately 400 vehicles equipped with a device that prevents acceleration when the vehicle is traveling faster than a preset threshold over the speed limit (typically 11 mph). Using an “opportunity to speed” framework (i.e., only account for driving time when a driver is traveling at least 5 mph below the speed limit), an analysis of 270 vehicles equipped with ISA showed there was a 64.18% relative decrease in the time driven >11 mph over the posted speed limit following ISA activation compared to before activation. This decrease in time spent speeding was not seen in non-equipped control vehicles. Speeding drive time reduction ranged from ~50% on 25 mph local roads, which have speed safety cameras set to the same enforced speed threshold, to 77% reduction on 50 mph roads. In addition, the impact of ISA on speeding behaviour of habitual speeders in 130 vehicles was similar to that on the primary cohort, indicating active ISA is effective at significantly reducing severe speeding across a wide range of drivers and fleets.