Healthy Development Measurement Toolkit

Indicator ST.1.g Number of motor vehicle collisions

Data Source

Geocoded data provided by the San Francisco Municipal Transportation Agency.  Raw data obtained from the California Highway Patrol, Statewide Integrated Traffic Records System (SWITRS). More information can be found at: http://www.chp.ca.gov/switrs/.

Map and table prepared by City and County of San Francisco, Department of Public Health, Environmental Health Section using ArcGIS software.

Map data is presented at the level of the census tract. The map also includes planning neighborhood names, in the vicinity of their corresponding census tracts.

Table data is presented by planning neighborhood. Planning neighborhoods are larger geographic areas then census tracts. SF DPH used ArcGIS software and a 'centroids within' methodology to convert census tracts to geographic mean center points. We then assigned census tracts to planning neighborhoods based on the spatial location of those geographic mean center points and calculated the planning neighborhood totals for the table.

Detailed information regarding census data, geographic units of analysis, their definitions, and their boundaries can be found in the HDMT at the following links:

http://www.thehdmt.org/etc/Geographic_Units_of_Analysis.pdf

http://www.thehdmt.org/data_map_methods.php

Explanation and Limitations

The California Highway Patrol defines "motor vehicle" as a mechanically or electrically powered device not operated on rails, upon which or by which any person or property may be transported or drawn upon a roadway. This would include motorized bicycles (mopeds).

According to the San Francisco Injury Center, San Francisco is a major tourist destination and employment hub for the Bay Area. The major corridors of the city have extremely high traffic volumes, and also tend to have high rates of vehicle-related injuries and deaths.

Notably, many individuals who may be in San Francisco do not reside within city limits (i.e., commuting employees, students, visitors and tourists). The San Francisco Injury Center estimates that in addition to the 469,000 vehicles registered to San Francisco residents and businesses, there are an estimated 435,000 vehicles that come in and out of San Francisco daily. The Center also estimates that 32% of hospitalizations in San Francisco hospitals are not for San Francisco residents, but rather visitors and guests, or persons transferred in from another hospital to SF for specialized medical care. (Profile of Injury in San Francisco, The San Francisco Injury Center and San Francisco Department of Public Health, December, 2004. Accessed online on October 26, 2006: http://www.surgery.ucsf.edu/sfic/profile05.pdf)

SWITRS data includes collisions on a public roadway that are reported to the California Highway Patrol. However, many collisions go unreported. Given San Francisco"s ethnic diversity, there may be certain neighborhoods which would be more or less likely to report injuries to authorities than others. For example, neighborhoods with higher immigrant densities may have lower reporting rates because of fear of deportation, whereas neighborhoods with a strong community police presence may be more likely to report collisions.

Why is this a Community Health Indicator?

Motor vehicle collisions are one of the leading causes of preventable injury in San Francisco, the nation, and the world, and the leading cause of death in the United States for people aged 1-24.^a