Are American Cities Making Progress on Traffic Safety?

Changes in traffic fatalities in selected cities with Vision Zero policies (rolling three-year averages indexed to 2010-12). The black line is the national trend.
Changes in traffic fatalities in selected cities with Vision Zero policies (rolling three-year averages indexed to 2010-12). The black line is the national trend.

Back in December we posted a chart of annual changes in traffic fatalities in six American cities that have adopted “Vision Zero” goals. There was no real discernible pattern, suggesting cities have yet to make much progress in reducing traffic deaths.

With data for 2017 now available, we updated the chart and added a few more cities. In several places, traffic fatalities fell much more sharply last year than in the nation as a whole. Does that mean Vision Zero policies are working? Well, it’s still too soon to tell.

Traffic deaths, especially in smaller cities like Portland, are subject to sizable year-to-year variation. A change in any given year doesn’t say much — only sustained reductions over a period of several years would indicate that Vision Zero policies are making an impact.

In Boston, traffic deaths fell in 2017 despite what advocates characterize as a lackluster commitment to traffic safety policies from Mayor Marty Walsh.

Stacy Thompson, executive director of Boston’s Livable Streets Alliance, said the decline in Boston was good news, but she hesitates to draw conclusions.

“It’s much like any public health trend,” she said. “This is a promising shift, but we need three to five more years of downward trends and analysis to fully understand if this is working.”

New York and San Francisco are the only two cities we tracked that have maintained a multi-year downward trend.

Like Thompson, San Francisco Bicycle Coalition Executive Director Brian Weidenmeier hesitates to draw conclusions.

“It’s an encouraging sign that 10 fewer people died on our roads,” he said, “But we need to make sure it’s a sustained effort.”

Most of the 2017 reduction in fatalities in San Francisco was among car occupants. There was one fewer bike fatality and the pedestrian death rate was largely unchanged, Weidenmeier said.

“Now is not the time to be less vigilant when it comes to investing in the kind of infrastructure improvements San Francisco needs to see,” he said.

One thing an exercise like this makes clear is the need for better traffic safety data. Fatalities are obviously the worst possible outcome and it makes sense to track them, but as a gauge of year-to-year traffic safety trends, the sample size is too small to reveal much, especially in smaller cities.

A better metric is to combine fatalities and severe injuries, which is less subject to random fluctuations.

Some cities do track progress this way, including Seattle. On the city’s open data website, you can look up the changes in fatalities and severe injuries indexed to population.

Seattle uses a five-year rolling average of traffic fatalities and serious injuries combined to track progress on traffic safety. Graph: Seattle
Seattle uses a five-year rolling average of traffic fatalities and serious injuries to track progress on traffic safety. Graph: Seattle

Unfortunately there’s often a significant lag before data on injury severity is finalized. And many cities don’t make it easy to get the information that is available. To get a better understanding of whether cities are making progress on their Vision Zero goals, the public will need better access to that data.

  • Would be interesting to see cities with VZ policies in one color, and a few cities without a policy in another color.

  • Streetsblog Network

    These are all vision zero cities but the national average is there too for comparison in black.

  • Baloo Uriza

    Wait, Portland is a “smaller city”? It’s the 26th largest city in the US, by itself, without the suburbs! There’s 19,328 smaller cities in the US alone! Portland’s a huge city, in the largest 0.002% of all cities nationally.

  • Would be nice to see specific peer cities: Miami to compare with Ft Lauderdale. LA to compare with SF. Seattle with Portland. (Assuming those dont have VZ)

  • Jeff

    Portland is not a “huge city”. If anything I’ll give you “mid-sized city”. Your numbers only make sense if you discount the colloquial use of words like “town” and “village”, and therefore insist on calling a gas station with a few houses scattered around in the middle of nowhere a “city”.

    If Portland is a “huge city”, what does that make New York and Philadelphia? “Incomprehensibly massive”?

  • Baloo Uriza

    Also huge cities.

  • SFnative74

    I would call SF a small city, and it has about 200,000 more people than Portland.

  • Stephen Simac

    these may be peer cities, but their traffic characteristics can differ greatly. Esp. LA to SF. I’m from Lauderdale originally and read both the Miami Herald and Ft. Laud. Sun Sentinel when I’m back there. Both have a huge problem with hit and run pedestrian fatalities, and there’s no respect for crosswalks.

  • Mike

    The pedestrian fatality rate has dropped every year since Vision Zero was initiated in San Francisco. 2014 saw 21 people killed while walking. 2015 – 20, 2016 – 16, 2017 – 14. Four straight years of drops – with an overall drop of 33% – is encouraging, especially at a time when the population has seen steady growth.

  • Edward

    The census bureau defines a “medium size city” as 50,000 to 500,000. Both San Francisco and Portland are large cities. In spite of what some of its inhabitants believe, Berkeley is a medium size city, not a village.

  • Baloo Uriza

    Heh, so Tulsa would be a medium size city, though I tend to think of 50-100k as a medium size city and anything past that as a large city.

    Berkeley? Who thinks of Berkeley as a village? I gotta wonder if folks that say this have been to Berkeley. That’s a pretty substantial city in it’s own right. A village would be I.X.L., Oklahoma…

  • Edward

    It is some of the NIMBYs in Berkeley who still believe it is a village. This wasn’t a serious comment on my part. Berkeley is now about 120,000 people and really needs to build some denser housing.

    There are 300 cities in California with a population between 10,000 and 100,000; 72 cities between 100,000 and 1 million and three cities over 1 million. Los Angeles at over 4 million is the third largest city in North America, after Mexico City and New York. Toronto is fourth.

    When I looked at the city list there were some over 100,000 that I had never heard of, and I was born here! This place just keeps growing.

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