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Creating a Data Resource of California Police Stops for Use in Traffic Safety Applications

Project Description

Traffic stops are one the most common ways in which the American public interacts with police. Although one of the leading reasons given for police traffic stops is a violation of the vehicle code, there is limited and mixed research on the impact of traditional police traffic enforcement on traffic safety outcomes. At present, few large data resources with an appropriate level of detail exist to facilitate investigations of this type. The 2015 Racial and Identity Profiling Act (RIPA) requires all law enforcement agencies in California to collect and submit vehicle (including bicycle) and pedestrian stop data to the State Department of Justice annually, starting no later than 2022. This project will use 2018-2022 confidential RIPA stop data to categorize all police traffic stops using known risk factors for fatal and severe collisions and to create new variables relevant to traffic safety, yielding a standardized statewide data set useful for examining and controlling for police traffic stops as they relate to traffic safety outcomes. Further, we will both establish clear guidance for how to process RIPA data efficiently for future data releases and will also will geospatially join the processed RIPA data files with traditional transportation and land use data sources using stop location so that this data resource can be made available to others for future research.


The project will yield a data file of processed and enriched police stop (RIPA) data for the State of California for the years 2018-2022. This resource will be tailored to the needs of researchers studying traffic safety, especially pedestrian and bicyclist safety. Lessons learned from the creation of this file will also be summarized and lead to the creation of a best practices document that will contain a how-to guide and accompanying code for data reduction steps.


A thorough examination of police traffic stops with an explicit link to known traffic safety risk factors can inform policy decisions and lead to changes in practice that will lead to safety improvements, as well as potentially decrease racial disparities often seen with traditional police traffic enforcement. This research will identify and highlight specific stop types that are clearly linked to traffic safety outcomes as well as identify stops that, while they may represent a violation of the vehicle code, don't actually have explicit ties to traffic safety. Elected officials and law enforcement and transportation agencies can use the categories of stops identified in this analysis to further refine any enforcement strategies they employ to take a step in ensuring that their traffic stop program is grounded in traffic safety reasoning.


06/01/2023 to 05/31/2024


University of California Berkeley

Principal Investigator

Julia Griswold

ORCID: 0000-0002-1125-3316

Research Project Funding

Federal: $63,669

Non-Federal: $0

Contract Number


Project Number


Research Priority

Promoting Safety

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