Study: Most of SF’s Severe Traffic Injuries Missing From Police Data

The number of severe traffic injuries inflicted on San Francisco's streets has been grossly underestimated, according to hospital researchers.

In one year, more than 60 percent of San Francisco's severe traffic injuries were missed by SFPD reports -- until now, the city's sole source of injury data -- according to a new study [PDF] by researchers at the SF Department of Public Health.

In the 12 months starting at the beginning of April, 2014, 515 patients were admitted for severe traffic injuries at SF General Hospital, site of the city's only trauma center. Police reports only accounted for about 200 of those injuries.

A person is severely injured in SF traffic every 17 hours on average, said Leilani Schwarcz, the epidemiologist who led the study as part of SFPDH's Vision Zero team. Of the 515 victims counted in the one-year period, 36 percent were pedestrians, 20 percent were bicyclists, 26 percent were motor vehicle occupants, and 17 percent were motorcyclists. Sixteen died.

The study defined "severe injuries" as cases where the victim was hospitalized for more than 24 hours. Of those, 10 percent are admitted to a skilled nursing facility for long-term recovery, as was the case for Monique Porsandeh in 2013.

"Those are the people that are most likely suffering long-term disabilities and physically or mentally-life changing events," said Walk SF Executive Director Nicole Ferrara, who said it's "really shocking that there are so many more life-changing injuries than we thought."

Schwarcz said the SFMTA funded the SFDPH study to develop a system that combines a range of data sources to more accurately assess the "true burden" of traffic violence. The agencies plan to conduct broader studies on the subject.

As for why so many traffic injuries have gone unreported, Schwarcz said that police officers "aren't trained medical professionals" and can't necessarily assess injuries fully. In addition, injuries are sustained on freeways, which are outside SFPD's jurisdiction, might not be counted by police. A small number of traffic injuries flagged by SFPDH may be due to solo bike crashes or collisions in BART tunnels, but not enough to account for a significant share of the discrepancy with SFPD's numbers.

Police reports were "never intended" to provide the sole basis for assessing the extent of traffic injuries, said Schwarcz.

Roughly 800 to 900 pedestrian crashes in total are reported every year, based on police reports. SFPD researchers have long suspected that at least 20 percent of pedestrian injuries go unreported, based on the volume of injuries seen at hospitals.

In 2011, an SFDPH study found that pedestrian injuries impose a cost of about $76 million a year, $15 million of which is for injury treatment alone.