Giving pedestrians a seven-second head start at traffic lights-known as Leading Pedestrian Intervals (LPIs)-is associated with a 33 percent reduction in total pedestrian injuries-both fatal and non-fatal-at New York City intersections, according to a new study by researchers at Columbia University Mailman School of Public Health.
The researchers analyzed data from 6,003 intersections-the largest dataset to date evaluating LPI effectiveness. The reduction in pedestrian injuries was consistent across all intersection types, with the most pronounced impact seen during the daytime: fatal pedestrian crashes dropped by 65 percent during daylight hours. The study was published in Nature Cities.
LPIs allow pedestrians to begin crossing before vehicles get a green light to turn, typically offering a 7- to 11-second lead depending on the intersection size.
"The idea is to give pedestrians time to reach the center of the intersection where they're more visible," said lead author Christopher Morrison, PhD, assistant professor of Epidemiology at Columbia Mailman School. "Most pedestrian-vehicle crashes happen near the curb, where drivers are less likely to see people crossing."
Using a spatial ecological panel design, the study evaluated intersection-level injury risk from 2013 to 2018, using precise geographic data from NYC Open Data and the city's Vision Zero initiative. Of the intersections studied, 2,869 had LPI treatments installed.
New York City was an early adopter of the U.S. Vision Zero program, a systems-based, multidisciplinary effort to reduce traffic-related injuries and deaths. LPIs-alongside other low-cost measures like speed humps and turn-calming treatments like rubber speed bumps-are central to the city's pedestrian safety strategy.
Globally, road traffic crashes cause more than 1.35 million deaths and 50 million injuries each year. In the U.S., over 68,000 pedestrian deaths and 6.1 million serious pedestrian injuries occurred between 2011 and 2020-many in large cities like New York.
The research team focused on pedestrian injuries occurring within 100 feet of a signalized intersection. Intersections within 10 feet of an LPI were categorized as treated; those beyond that buffer were considered untreated.
"As someone who lives in the city, it is good to know that interventions like LPIs led by NYCDOT are making pedestrians safe", noted co-author Siddhesh (Sid) Zadey, doctoral student in Epidemiology at Columbia Mailman School.
"LPIs are one of the most affordable and scalable traffic safety interventions," Morrison added. "A 7-second delay for drivers can mean the difference between life and death for pedestrians. Our findings show they work-and should be adopted more widely."
Other co-authors include Leah Roberts, Brady Bushover, Arianna Gobaud, Christina Mehranbod, Carolyn Fish, Xiang Gao, Evan Eschliman, and Dana Goin-all from Columbia University Mailman School of Public Health.
Funding was provided by the CDC's National Center for Injury Prevention and Control (Grant R49CE003094) and the National Institute on Drug Abuse (Grant T32DA031099).
