SR 91 is a heavily traveled east-west corridor through Riverside and Orange Counties, California. Currently, SR 91 includes two tolled express lanes in each direction in Orange County from the Riverside County line 10 miles west to Anaheim. They are managed by the Orange County Transportation Authority. The SR 91 Corridor Improvement Project will extend the tolled express lanes west into Riverside County from the Orange County line to I-15, a distance of approximately eight miles, replacing the existing High Occupancy Vehicle (HOV) lanes. The project will also add one general purpose in each direction and make improvements to bridges and interchanges, including the addition of auxiliary or merge lanes for improved access. Direct connectors to/from the express lanes to I-15 south of SR 91 are also included.

SR-91 is currently used by more than 280,000 vehicles per day, and this volume is expected to increase by approximately 50 percent by 2035. According to the RCTC, the project is estimated to create approximately 16,200 jobs and $310 million in total economic impact. The finished improvements will accommodate growing demand, featuring a fully electronic tolling system designed to prevent significant traffic delays and improve corridor safety. According to the RCTC, the project is forecasted to reduce the average daily trip by 30 minutes, resulting in an estimated value of $36.3 million in annual travel time savings. The improvements are also expected to reduce fuel consumption by approximately 285 million gallons and eliminate roughly 2.1 million tons of carbon dioxide emissions over the 50 years. TIFIA financing allows for the realization of these benefits at least two years faster and at cost reductions of approximately $749 million when compared to the timeline and cost of conventional financing methods.