San Diego’s Interstate 15 Congestion Pricing Project: Traffic-Related Issues

Traffic-related findings from the evaluation of the Interstate 15 (I-15) congestion pricing project are summarized. The project was a 3-year demonstration that allowed single-occupant vehicles (SOVs) to use the existing I-15 high-occupancy-vehicle (HOV) lanes, known as the I-15 express lanes, for a fee. San Diego State University conducted an independent, multielement evaluation of the I-15 pricing project to assess its impacts for both the ExpressPass and FasTrak phases of this demonstration. The primary project goals were ( a) to maximize use of the existing I-15 express lanes, ( b) to test whether allowing solo drivers to use the express lanes’ excess capacity could help relieve congestion on the I-15 main lanes, ( c) to fund new transit and HOV improvements in the I-15 corridor, and ( d) to use a market-based approach to set tolls. At the end of 1999, the I-15 pricing project was meeting its primary objectives. There was substantially better utilization of the express lanes. Both ExpressPass and FasTrak were feasible solutions for generating sufficient revenue to fund the new express bus service, called Inland Breeze. Neither ExpressPass nor FasTrak negatively affected carpool volumes on the express lanes; FasTrak was able to redistribute volumes from the middle of the peak to the peak shoulders. Free-flow conditions were maintained at virtually all times. The project’s primary benefit was the reliability of ontime arrival for users. The project was also able to slightly alleviate congestion on the I-15 main lanes. SOV violation rates in the I-15 express lanes remained substantially below the preproject level. Also discussed are the air quality, delay, and park-and-ride impacts of the project.