Developing a Safe System Approach to Setting Speed Limits

The objective of this research is to develop preliminary technical requirements for a Safe System approach to setting speed limits in California. In the previous phase of the research, New Zealand’s approach was identified as appropriate for implementation in California. The technical requirements include developing a context-sensitive street category framework, determining safe and appropriate speed limits for each category, and identifying an appropriate infrastructure risk assessment methodology. The desired outcome is a knowledge-driven analysis resulting in the development of preliminary technical requirements that will lay the foundation for implementing a Safe System approach and advancing the State in its goal of Toward Zero Traffic Deaths.

Start Date: April 1, 2024
Completion Date: May 31, 2026

Transportation professionals and policy makers in California are confronting a growing problem: increases in road traffic fatalities, injuries, and crashes despite a commitment to safety. In California, nearly 3,600 people die each year in traffic crashes and more than 13,000 people are severely injured. Collectively, these traffic crashes cost California over $53.5 billion, and speeding-related fatalities continue to represent a large portion of California’s total traffic fatalities. Recent research has demonstrated that speed increases crash risk in two ways: it increases the likelihood of being involved in a crash and it increases the severity of injuries sustained by all road users in a crash. 

In California, the relationship between speed and crash involvement has prompted calls from local governments to change the way that speed limits are set. In response, the Legislature passed Assembly Bill 2363, which directed the California State Transportation Agency (CalSTA) to convene a Zero Traffic Fatalities Task Force (ZTFTF) comprised of experts from across the state to brainstorm, evaluate, and recommend alternatives to the current speed-limit-setting methodology. 

This research project represents the first step towards developing a Safe Systems approach to setting speed limits, per CalSTA’s recommendation. The Safe Systems approach is used in other countries, most notably Sweden, the Netherlands, and Australia, and has been studied extensively. But it has yet to be implemented in North America. Changing how California establishes speed limits will be a significant undertaking that will require funding, time, and expertise to facilitate strategic decision and policy-making. 

Start Date: January 1, 2021
Completion Date: June 30, 2023

Project Resources

• DRISI Research Project Notes: Developing a Safe System Approach to Setting Speed Limits (May 2023)