Healthy Development Measurement Toolkit

Indicator ST.3.c Number of bicycle collisions

Data Source

Geocoded data provided by the San Francisco Municipal Transportation Agency.  Raw data obtained from 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.September_2009.pdf

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

Explanation and Limitations

The Vehicle-Bicycle collisions reported above are those involving at least one bicyclist as well as a motor vehicle driver as another party in the collision.

According to the San Francisco Injury Center, San Francisco is a major tourist destination and employment hub for the Bay Area. The major transportation corridors of the city have high traffic volumes, and are often where bicycle-involved injuries and deaths occur.

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, and include visitors and guests in addition to 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.)

This data relies on bicycle collisions that are reported. 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 population 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.

The San Francisco Municipal Transportation Agency's (SFMTA) Planning Division released its first report on Bicycle Injury Collisions (February 2008), primarily based on 2005-2006 data, which can be accessed at: http://www.sfmta.com/cms/rbikes/documents/CollisionReportFINAL2_2008.doc.  The SFMTA also recently released a "State of Cycling" Report (2008), "developed to provide a snapshot of cycling in San Francisco and to identify ways that the SFMTA can increase safe bicycling," which can be accessed at:  http://www.sfmta.com/cms/rbikes/documents/2008SFStateofCyclingReport.pdf.

Why is this a Community Health Indicator?

Motor vehicle crashes are one of the leading causes of preventable injury in San Francisco and the nation, and the leading cause of death for people aged 1-24.^a Changes in the roadway environment can address both real and perceived safety hazards for bicylists - including adding bicycle lanes, reducing vehicle speeds (traffic calming), and introducing additional traffic engineering measures at intersections (e.g., signs, turning restrictions) to reduce conflicts between bikes and cars.^b Other interventions to reduce deaths and serious injuries include use of bicycle helmets and increased driver and bicyclist education. Ensuring real and perceived safety for bicycle riders is necessary to encourage bicycle travel, an active travel mode that does not contribute to air pollution or green house gas emissions and has physical and mental health benefits.