A hallmark of Vision Zero, the multinational policy platform to eliminate traffic deaths, is its emphasis on numbers. Austin, San Francisco, Los Angeles, and many other cities describe how they target corridors for safer street engineering, driver education, speed limit reductions and other interventions with the phrase “data-driven.”
The problem is that the data driving such efforts are rarely, if ever, complete. Most cities rely on local police to record car crashes, including those involving pedestrians and cyclists who are often the focus of Vision Zero programs. But sometimes police officers are never called or never show up. Those involved in a crash may leave rather than waiting for authorities arrive, or they might refuse assistance. That leaves gaps in official knowledge of where traffic dangers lie, which inform Vision Zero efforts to fix them.
Tech-savvy safety advocates in Washington, D.C., came up with an innovative way to fill in some of those blanks. Earlier this year, Charlotte Jackson, a D.C. resident and data scientist, listened to six weeks of local 911 calls on the open-source police scanner website OpenMHZ.com and Pulsepoint, an app that tracks police and emergency responders, to find out how many crashes were left out of Metropolitan Police Department data, which is used by District transportation officials.
Comparing what she heard in the calls to official MPD counts from March 18 to April 30, she found that 265 out of a total of 2,572 vehicle-only crashes, or about 10%, did not end up in MPD’s official crash ledger. For the 236 collisions that involved a person outside a vehicle — meaning a cyclist or pedestrian — 71 were unreported, or 30%. In other words, pedestrian and bike crashes were three times more likely to be left out of the city’s official crash count — echoing a common complaint in the cyclist community that police attention has a bias toward motor vehicles.
Where Pedestrian Crashes Go Undetected in D.C.
D.C. police data fails to capture more crashes in predominantly Black wards
Data: Charlotte Jackson/Code for D.C. Crash counts cover May 15-July 12 2021.
What’s more, certain parts of the city had much higher rates of unreported collisions. On a public data dashboard that Jackson built with Theo Goetemann, founder of analytics startup Basil Labs, more recent numbers covering May 15 to July 12 show that in Wards 7 and 8 — where more than 90% of residents are Black — nearly 37% and 35% of crashes went undetected by the powers-that-be. That could be due to the extremely high levels of distrust in police harbored in many Black communities, Jackson said. Those areas then may not receive the level of attention to safety that they should, perpetuating a lack of investments and disproportionate rates of traffic violence long seen in neighborhoods of color, which often lack street improvements like protected bike lanes and pedestrian infrastructure.
“When someone in Ward 7 submits a traffic safety request, the city will look at the statistics and make a decision on whether to act,” she said. “But the correct urgency just will not be there because nearly 40% of crashes never happened, as far as they are concerned.”
Elaina Gertz, a spokesperson for the Metropolitan Police Department, said she could not comment on Jackson’s data without additional information about how she collected it. Asked about the broader issue of underreporting, she said that if someone is involved in a traffic accident, they should report it to MPD. “That’s the only way we know if an accident occurred for traffic safety planning purposes,” she said. The District Department of Transportation did not respond to a request for comment in time for publication.
Now, Jackson and her colleagues have set up a software program that automatically scrapes emergency call data as well as data from Twitter and other sources to produce a daily count of reported versus unreported crashes. She said the hope is that this work can be replicated by groups in other cities.
It’s not the only effort out there to expand the Vision Zero data universe as many U.S. cities have struggled to reduce traffic deaths, even during the pandemic. San Francisco’s departments of public health and transportation have pioneered an effort to join police crash data with hospital case data. New York City puts telematics on city vehicles that can detect and help reconstruct collisions, while the automaker Ford is working with Michigan State University to test whether connected vehicle technology can be used to transmit crash data to cities faster than police can. Philadelphia officials conducted extensive public outreach to inform a recent Vision Zero strategy update instead of relying on numbers alone, said Leah Shahum, founder and director of the Vision Zero Network, a clearinghouse for traffic safety strategies.
“How do we measure and have accountability for states and cities around traffic safety?” Shahum said. “We need to do that now before we have perfect data. But there is a real understanding now that using only police data is not sufficient.”