research >>geocoding crash data

Using GIS to Identify Clusters of DUI Crashes

TIMS (Transportation Injury Mapping System)

A review of the spatial accuracy of FARS coordinate locations in California

FARS records were matched to a random selection of 100 fatal collisions from SWITRS using dates, times, street intersections and postmile information to provide necessary locational information for reviewing. Collision records were exported to Google Earth to measure the positional accuracy within 300 feet.

Results:81 collisions were correctly geocoded, 12 were incorrect and seven were unknown. Locations on non-state highways were correctly matched 86% of the time, while crashes on state highways matched only 76% correctly. Rural state routes had lower match success than more urbanized areas.

Conclusions:This research shows that there are discrepancies that should be considered when using the FARS coordinate locations and provides support for the incorporation of GPS technology to complement written location descriptions in the future.

A review of the spatial accuracy of FARS coordinate locations in California, poster presentation for the APHA 2010 annual meeting.

Slides presented at SafeTREC seminar for students' work summer 2009.

State-Level Geocoding of SWITRS Data

Geocoding the data gathered by the Statewide Integrated Traffic Records System (SWITRS), the primary source of state-level crash data for California agencies, would significantly enhance the data's usefulness in targeting traffic safety programs and evaluating safety measures' effectiveness. But there are many barriers to achieving this objective, including lack of standardized hardware and the high cost of institutional changes in how data is recorded and transmitted and of ensuring the data is accurate.

A web-based tool to query and map police collision report data

SWITRS data obtained and geocoded in an earlier project were stored in a MySQL database. A query system was designed using Apache web server, PHP programming language, JavaScript, and Google Maps. A point-and-click interface allows users to select collision records as defined by numerous factors. Results can be downloaded. The tool may lower barriers to California traffic collision data and increase the use of empirical data in traffic injury prevention activities.

SafeTREC Resources

A web-based tool to query and map police collision report data
Thomas M. Rice, John M. Bigham, Jiyeon Lee, Shin-Hyoung Park, TSC
Presented at the 2009 Annual Meeting of the American Public Health Association, November 7-11, 2009, Philadelphia.

"A comprehensive approach to geocoding collisions from the California Statewide Integrated Traffic Records System (download PDF of PowerPoint™ presentation—600K)," presented by John Bigham, MPH, GSR at the UC Berkeley Traffic Safety Center. May 2008.

One of the geocoding adjustments that needs to be made is differentiating between the different branches of bi-directional streets, like Shattuck Ave. in north Berkeley (left). Click on image for larger view.

Using multiple software applications and custom code, TSC has developed a methodology and work flow that takes full advantage of all location information available for collisions in SWITRS. The end result allows more collisions to be geocoded in a more precise manner than previous efforts.

An aerial photo of the same stretch of Shattuck Ave. Click on image for larger view.

"Zeroing in on Drinking-Driving, Mapping, Data Analysis, and Surveys Help Highlight Problems and Reduce Risk," TSC Online Newsletter, Winter 05-06.

"State-Level Geocoding of SWITRS Data," Proposal Outline, by David R. Ragland.