Can this crosswalk change improve safety? New study yields promising results

SALT LAKE CITY — A few years ago, as Utah dealt with an uptick in roadway fatalities, Salt Lake City’s transportation division began tinkering with the timing of crosswalk signals based on an emerging new concept.

A few other U.S. cities had installed leading pedestrian intervals, or LPIs, as a potential solution to improve traffic safety. The traffic signal technology gives pedestrians a slight head start at a crosswalk. Most of the research had been preliminary to that point, leading to “mixed” results on whether it worked, but the idea seemed intriguing enough to test, said Salt Lake City transportation director Jon Larsen, as he recalled those conversations.

By allowing pedestrians to start moving 3 to 7 seconds before the traffic signal, many can cross the intersection or reach the midpoint. At the very least, it can give people time to be more visible in a crosswalk.

“Giving pedestrians a head start so they’re able to cross when all of the traffic has stopped — it just intuitively makes sense,” he said.

Now, a few years later, a recently released study offers hope that Salt Lake City made a good investment.

Installing LPIs curbed total injuries — fatal and nonfatal alike — by one-third when implemented in New York City, researchers at Columbia University’s Mailman School of Public Health found in a study published in Nature Cities last month.

The finding is based on a review of data at over 6,000 intersections from 2013 to 2018, nearly half of which had LPIs, representing the largest collection of intersections reviewed in a study to date. The total number of pedestrian injuries plummeted when the crosswalk signal started seven seconds before the traffic signal, while the number of daytime fatal pedestrian crashes also dropped by 65%.

They determined that it’s an “effective intervention to improve pedestrian safety,” especially in urban communities. It could help reduce the number of pedestrian deaths and injuries, which — as they point out — totaled 68,000 deaths and 6.1 million serious injuries in the U.S. between 2011 and 2020.

“LPIs are one of the most affordable and scalable traffic safety interventions. … Our findings show they work — and could be adopted more widely,” said Christopher Morrison, assistant professor of epidemiology at Columbia Mailman School, and the study’s lead author, in a statement.

Salt Lake’s dive into LPIs

Salt Lake City began installing LPIs about two or three years ago. Mayor Erin Mendenhall announced the formation of a safety task force that would look into ways to reduce traffic crashes in 2022. She and Utah Department of Transportation director Carlos Braceras were concerned by a spike in fatal crashes across the Wasatch Front, and they wanted to explore potential solutions.

The city ultimately joined the Vision Zero Network — a collaborative that seeks to find ways to reduce traffic-related fatalities and severe injuries — a year later, after 26 people died in traffic crashes in 2022. Delayed signaling was one of the options it could explore, city leaders explained at the time.

Larsen reviewed Columbia’s study and says the results are promising.

“It is nice that it is finally getting studied, and we’re starting to see some of the benefits,” he told KSL.com.

Fifty-three of the 213 traffic signals that Salt Lake City manages now have LPIs, and the city wants to install them at the remaining intersections. It’s still too early to determine if this change is making the same level of injury prevention as what Columbia researchers found. That’s something the city plans to track moving forward.

Effectiveness may differ from intersection to intersection, Larsen said. LPIs could be more effective on smaller, narrower streets that take less time to cross, as opposed to larger streets that take longer to cross and often draw in larger traffic.

There are other limitations when it comes to reducing pedestrian injuries and deaths, including cases where someone may cross an intersection against the right-of-way. Nearly three-fourths of pedestrian deaths in 2018 also happened away from an intersection in other parts of the road, according to the Federal Highway Administration.

Salt Lake City has implemented other safety measures in recent years, including slower speed limits on many roads, with the hope of reducing injury severity in other scenarios.

A quiet solution?

Meanwhile, other recent studies suggest that LPIs don’t have much of an impact on traffic.

The transportation research firm Kittelson & Associates reported last year that it found “minor to no additional vehicular delays” after partnering with the Florida Department of Transportation on a study of 16 different intersection models with LPIs.

To that end, LPIs have flown mostly under the radar to this point in Salt Lake City. The little feedback the city has received on the technology — mostly from pedestrians or crossing guards — has been generally positive.

Larsen suspects it’s because many people may not have noticed the difference.

“A lot of people — I don’t think — really realize that it’s happening,” he said. “A lot of drivers just pay attention to the light in front of them when it’s red and green.”