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Speed limits and pedestrian fatalities

Here’s a topic that won’t be the least bit controversial, I’m sure.

The New York City Vision Zero goal is simple and precise: to end traffic deaths and injuries on city streets. This is not a mere sound bite in New York City. Mayor Bill de Blasio launched his Vision Zero initiative before he took office and is moving the transportation safety work started by his predecessors, Mayor Michael Bloomberg and Transportation Commissioner Janette Sadik-Kahn.

Polly Trottenberg, the current New York City Transportation Commissioner, was an opening speaker at the inaugural Vision Zero for Cities Symposium in mid-November where she restated her commitment to safety for all transportation modes, including walking and cycling.

The symposium, organized by Transportation Alternatives, brought together 300 government and non-government participants from dozens of cities across the U.S. and the world. Transportation Alternatives is a grassroots organization that has worked for decades to improve cycling and walking safety in New York City. It reached a major milestone in 2013 when the city adopted the Vision Zero Action Plan. The 10-year plan sets a high bar through better street design and changing road user behavior. The details are as complex and comprehensive as you might expect for a plan that will create sweeping cultural and engineering changes to the nation’s largest city, but it is built on two fundamental principles: Reduce the chance of collisions and reduce injury by reducing speed.

The myths about New York City transportation safety defy the facts. A popular myth is that New York streets are dangerous, but the fact is their streets are far safer than San Antonio’s streets. In 2012, there were 268 deaths from traffic violence in New York City. Of those, 127 pedestrians and cyclists were killed. During the same period, San Antonio traffic fatalities per capita were 297% that of New York City, and pedestrian/cyclist fatalities per capita were 176% greater that of New York City, according to 2012 National Highway Traffic Safety Administration numbers.

New York City outperforms San Antonio, and almost every other city in the nation, in traffic safety. Yet, the overwhelming majority of New Yorkers share San Antonio’s culture of indifference to traffic deaths. However, a growing group of transportation safety activists throughout New York City steadily chipped away at that indifference and in the past 24 months made powerful breakthroughs. First was the adoption of Vision Zero, followed by establishment of Families for Safe Streets. Families for Safe Streets is a coalition of families who lost a child, parent, or spouse in a pedestrian or cycling collision with an automobile. Families for Safe Streets was a powerful, watershed organization, but one that no one wants membership in.

The establishment of Families for Safe Streets was a pivotal step. Their tragic stories, their conviction to ending this culture of indifference compelled the state legislature to pass a bill permitting New York City to set a city-wide default 25-mph speed limit. The Metropolitan Taxicab Board of Trade, a taxi trade association, has joined as partners. Major arterials are being converted to 25-mph speed zones. Streets and intersections throughout the city are being redesigned to reduce chaos, instill discipline, and convert automobile lanes to dedicated cycling and pedestrian uses.

It’s the citywide 25 MPH speed limit that I’m sure will give everyone reading this heartburn. Author Kevin Barton discussed that topic in an earlier post in which he notes that on military bases, in San Antonio and around the country, where speed limits in housing areas are 20 MPH and more rigorously enforced, there are essentially zero traffic fatalities. This Wired article goes into some detail:

“I’d estimate that a person is about 74 percent more likely to be killed if they’re struck by vehicles traveling at 30 mph than at 25 mph,” says Brian Tefft, a researcher with the AAA Foundation for Traffic Safety who wrote a 2011 report on the subject. He looked at 549 vehicle-pedestrian accidents occurring across the US between 1994 and 1998, accounting for factors like vehicle size and pedestrian BMI. The risk of serious injury (defined as likely to result in long-term disability) for a pedestrian hit at 23 mph was about 25 percent. At 39 mph, it jumped to 75 percent. Analyzing his findings, Tefft says, “25 to 35 mph, they’re almost three times as likely to be killed.” 35 mph, he found, was the median impact speed for fatal pedestrian crashes.

A 2010 study in London had similar findings: “In all of the pedestrian datasets, the risk of fatality increases slowly until impact speeds of around 30 mph. Above this speed, risk increases rapidly – the increase is between 3.5 and 5.5 times from 30 mph to 40 mph,” the author, D.C. Richards, writes.

So why doesn’t a 20 percent change in speed just mean a 20 percent change in serious injuries? There are lots of variables at work here (is the car an Escalade or a Fiat? is it a direct hit or a side swipe?), but, it turns out, the 30 mph mark is something of a limit for what our bodies can live through. Above that speed, organs and the skull aren’t necessarily strong enough to withstand the kinetic impact of a bumper and windshield.

“It has to do with fracture forces,” says Dr. Peter Orner, a licensed physician and former engineering professor who consults on injury biomechanics in car crashes. “As velocity increases, you’re crossing thresholds.” Though he’s skeptical of the comprehensiveness of studies like Tefft’s, Orner also says that at higher speeds, “the car is going to scoop them up.” And when you’re talking about cars, what gets scooped up is usually smacked against a windshield or thrown onto the ground. That can easily lead to brain trauma.

This Smart Growth America report on how dangerous various cities are for pedestrians tells us that for the period of 2003 through 2012, there were 1,073 pedestrian fatalities in the Houston-Baytown-Sugar Land MSA. Granting that that’s a large population, it’s still a lot of dead people, and that doesn’t include bicyclists and passengers or drivers of motor vehicles. I feel reasonably sure if you put all that together the total would exceed the equivalent tally for homicides, yet somehow it gets much, much less attention. Lower speed limits in residential areas, combined with tighter enforcement, could have a large effect on that, and I say this as someone whose driving habits would most definitely be affected. It’s a subject that deserves some discussion. Here’s some further information about Vision Zero in New York, and an assessment of how the first year of it has gone. What do you think?

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