The Costa Mesa (SR-55) Freeway is one of the most heavily congested freeways in Southern California, and future demand is only expected to increase congestion. The SR-55 serves as a vital link to other major freeway systems within Orange County, and it is the only freeway providing a direct north-south connection between Central Orange County and the Coastal Region. Currently, the SR-55 between Interstate 5 (I-5) and State Route 91 (SR-91) has three to four general purpose lanes, one carpool lane and some auxiliary lanes in each direction. This project proposes to improve mobility and reduce congestion, increase freeway capacity and improve traffic operations.