Crash data driving city safety efforts is incomplete

in July 23rd, 2021

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If a crash isn't reported, did it really happen? It’s a good question when looking at the work done by Vision Zero, an initiative started in 1997 aimed at eliminating traffic deaths by working with a diverse set of stakeholders to recommend safety fixes for everything from speed limits to street engineering. Now, Vision Zero is a global network of cities committed to making those safety fixes using hard data.

Problem is, they rely on local police to record car crashes, which a new analysis proves can be an incomplete data source. The analysis compared what was heard in Washington, D.C.’s open police scanners to its official crash ledgers and found that: 

  • 10% of vehicle-only crashes did not appear in official crash ledgers managed by local police from March 18 to April 30
  • Specifically looking at car crashes with a cyclist or pedestrian, 30% of those crashes went unreported, a major concern as fatalities in such crashes are on the rise, even in Vision Zero cities
  • Both scenarios worsen in predominantly Black neighborhoods where up to 37% of crashes did not appear in their respective crash ledgers — possibly due to distrust, as illustrated in a 2016 study where Black neighborhoods saw a drop in 911 calls following police violence against unarmed Black men

Now, a daily count of unreported crashes is available through software that automates the analysis with an expanded set of other sources such as Twitter. Both this software and original findings were born out of a collaborative investigation from safety advocates, including Basil Labs who published the report, with the hope that cities will follow suit — especially as traffic fatalities rise even through the pandemic. 

Some cities are already waking up to the pitfalls of narrow data sources and are working to expand the Vision Zero data universe. For example, San Francisco’s department of public health and transportation are supplementing data from police with hospital case data. And in New York City, city vehicles detect collisions through the use of telematics (a method of monitoring).


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