Gaining Wait? Analyzing the Congestion Impacts of Road Diets in Los Angeles

As part of the Cityís Vision Zero policy goal put forth by Mayor Eric Garcetti in 2015 to eliminate traffic related deaths on city streets, the Los Angeles Department of Transportation (LADOT) has reconfigured a number of stretches of roadway in the city, removing lanes and installing what are commonly known as ìroad diets.î While numerous studies have shown road diets can greatly reduce the number and severity of collisions, especially for pedestrians and cyclists, the public response to many of the changes implemented in Los Angeles has been quite negative. The Active Transportation and Special Programs (ATSP) team of the Southern California Association of Governments (SCAG), the Metropolitan Planning Organization for the Southern California region, has a strong interest in improving traffic safety in the region, and seeks research to determine if the proven safety improvement measures known as road diets cause the delays and increases in congestion that many opponents claim. To examine this issue I survey existing literature on road diets and their congestion impacts, analyze before and after LADOT daily traffic volume data for four street segments where the city installed road diets and nearby parallel segments where no change was made, and observe current conditions of ten intersections within the selected street segments to assess potential ongoing delay and congestion in the study corridors. This analysis finds an overall increase in traffic volumes of 8 percent on the selected road diet corridors, while volumes decreased very slightly on nearby parallel control corridors. Supplemental field observations of representative intersections for each of the four road diet corridors and their respective control corridors suggest that current lane configurations have not negatively affected peak-hour traffic flow or level of service on either the road diet or control corridor