Connected Vehicle Speed Limit Warnings Increased Speed Compliance by 16 Percent During a Pilot Test in New York City.

USDOT Assessment of Connected Vehicle Safety Applications.

Date Posted

Safety Impact Assessment of New York City Connected Vehicle Pilot Safety Applications

Summary Information

The New York City Department of Transportation (NYCDOT) worked with the United States Department of Transportation (USDOT) to implement real-time Vehicle-to-Infrastructure (V2I), and Vehicle-to-Vehicle (V2V) communications under the Connected Vehicle Pilot Deployment Program (CVPD). The safety impact of five V2V and four V2I safety applications deployed in NYC’s Connected Vehicle Pilot site were assessed. The V2V applications included Forward Collision Warning (FCW), Emergency Electronic Brake Light (EEBL), Lane Change Warning (LCW), Blind Spot Warning (BSW), and Intersection Movement Assist (IMA). Speed Compliance (SPDCOMP), Curve Speed Compliance (CSPDCOMP), Speed Compliance in Work Zone (SPDCOMPWZ) and Red Light Violation Warning (RLVW) comprised the V2I applications. This assessment was based on data collected around 160,289 alert events from the naturalistic driving experience of 3,000 vehicles that were equipped with these applications, during January to December of 2021.


The deployed vehicles experienced 107,609 alerts by V2I applications and 52,680 by V2V applications. Of all these events, 65,231 alerts were silent and 95,058 alerts were active. After data filtering and validation, the analysis broke down the events with valid alerts by treatment and control groups, before and after deployment periods, and silent and active alerts. The analysis identified and statistically described vehicle/driver response measures after alert onset for each application, including statistical tests to reveal any statistically significant differences in any of these measures between two experimental groups. Due to data limitation, the final safety assessment was achieved by comparing the response between all valid events with silent alerts and all valid events with active alerts, regardless of period (before or after) or vehicle group (treatment or control). The deployment was evaluated considering a “before” period from January 1 to May 19, 2021 and an “after” period from May 20 to December 31, 2021 using statistical comparisons between experimental groups.


Based on the statistically significant difference in vehicle/driver response between events with silent and active alerts for each safety application, the key findings were summarized in Table 1.

Table 1. Statistical Results of Safety Impact Assessment of the NYC CVPD Applications.

Connected Vehicle Application


Key Finding



16-percent increase in speed limit compliance



41-percent reduction in red light violation rate; Reduction in brake reaction time by 0.4 s



Reduction in minimum speed by 3.6 m/s; Increase in speed differential by 1.5 m/s



Increase in minimum speed of 0.2 m/s; Decrease in speed differential by 0.2 m/s



25 percent reduction in near-crash rate in the Lead Vehicle Decelerating (LVD) scenario; Reduction in brake reaction time in the LVD scenario by 0.13 s



Reduction in brake reaction time by 0.4 s; Reduction in average deceleration by 0.17 m/s2



46 percent reduction in unsafe lane change rate; 12 percent reduction in lane change rate



77 percent reduction in unsafe lane change rate



Reduction in brake reaction time by 1.3 s

The increase in speed limit compliance by SPDCOMP, reduction in red light violation rate by RLVW, reduction in near-crash rate in the LVD scenario by FCW, reduction in lane change rate by LCW, and reduction in unsafe lane change rate by LCW and BSW directly lead to potential safety benefits and the reduction in brake reaction time due to RLVW, FCW, EEBL, and IMA applications indirectly contributes to potential safety benefits from their deployment.



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Results Type
Deployment Locations