By Chris McCahill
High-speed travel in urban areas poses many risks, including a narrower field of vision, longer stopping distances, and increased risk of injury during a collision. According to a new study published by the Transportation Research Board, however, drivers traveling at higher speeds are also far less likely to yield to pedestrians in crosswalks. The study, conducted in Boston, reveals that drivers are nearly four times more likely to yield for pedestrians at travel speeds around 20 miles per hour than at 40 mph.
The researchers observed 100 attempted crossings at each of nine marked crosswalks. All but one of the sites were two-lane streets, most had on-street parking, and most were in residential areas. Three of the streets also had commercial uses.
The sites were divided into three groups based on their 85th-percentile speeds. At 20 mph, roughly 75 percent of drivers slowed enough to let pedestrians cross. That rate dropped to around 40 percent at 30 mph and less than 20 percent as speeds approached 40 mph. The researchers also found that for eight of the sites (excluding the only four-lane street), travel speeds explained 99 percent of the variation in yield rates.
These findings bolster the case for more stringent speed enforcement, which many cities now include in their pedestrian safety initiatives. However, Tom Bertulis, an engineer in the Boston area and the study’s lead author, says this work can also improve the way designers deal with unsafe crossings. “I would like to think that it opens up options for folks,” he told SSTI. “Previously the emphasis has been on either putting down a traffic control device or not, due to various constraints. But now there’s hopefully increasing emphasis on also reducing speeds, whether it is through skinny lanes, signal coordination at 25 mph, or actually putting traffic calming devices on arterial roadways.”
Chris McCahill is a Senior Associate at SSTI.