Evaluating the Safety of Adopting a Stop-as-Yield Law for Cyclists in California

Research Team: Julia Griswold (lead), Iman Mahdinia, Rafael Unda, Soheil Sohrabi, and Offer Grembek

UC Campus(es): UC Berkeley

Problem Statement: Cycling is an affordable and sustainable mode of travel to mitigate traffic congestion, reduce air pollution, and complement public transport in cities. It increases physical activity and promotes public health. “Bike-friendly” laws such as Idaho’s 1982 Stop Law (Idaho Statutes § 49-720) allows cyclists to treat stop signs as yield signs and red traffic lights as stop signs, allowing riders to maintain their energy and momentum. Laws such as these that legitimize common cycling behavior can encourage people to use this environmental-friendly mode of transportation, and may also free up the courts’ time by eliminating certain minor traffic offenses. Nine states have laws similar to the Idaho Stop Law, however, there is limited research on how or whether these laws affect traffic safety, particularly in large urban areas.

Project Description: This study investigates how stop-as-yield laws can positively or negatively affect safety and provides insights and guidelines for California policymakers and safety practitioners if such a law passes in California. The research team collected cyclist data from five states that enacted stop-as-yield laws—Idaho, Arkansas, Oregon, Washington and Delaware—and data from some of their contiguous states without such legislation. Using an observational before-after study with comparison groups at the state level, the research examined changes in cyclist crash frequencies after the laws were implemented. Additionally, a random-effects negative binomial regression model with panel data was employed to estimate a law’s overall impact. The results did not indicate a significant change in cyclist crashes among the states with stop-as-yield laws.

Status: Completed

Budget: $80,000