A California Department of Transportation (Caltrans) funded study with the Cleveland National Forest Foundation (CNFF) concluded that making more improvements to the Los Angeles - San Diego - San Luis Obispo (LOSSAN) corridor, could make using public transportation on this route faster and more affordable than driving a car. It could also reduce greenhouse gas emissions. The study examined the feasibility of building a double-track tunnel through Miramar Hill and a multimodal transit station at the University Town Center in San Diego.

Realigning the LOSSAN line by constructing a tunnel under the Miramar Hill would shorten the rail route between Los Angeles and San Diego by approximately three miles and reduce travel time by six to seven minutes. The transit center would provide connection to light rail, local bus, and bus rapid transit, as well as local bicycle and pedestrian access, making it easier for train travelers to access transit options in the San Diego area.

The feasibility study concluded that the proposed Miramar Tunnel project would successfully meet the four settlement agreement criteria for feasibility. These criteria include:

1. Increasing discretionary passengers. The study found the project would lead to an increase of 1,300 to 1,700 discretionary passengers per day, thereby reducing annual greenhouse gas emissions by 70,000 to 84,000 metric tons.

2. Providing competitive travel times. The study found the project would decrease train travel times between Los Angeles and San Diego to an average of 3% faster than automobile travel at peak hours.

3. Being cost competitive with car travel. The study concluded that transit rider cost would be $180 per month vs $507 per month for driving a car.

4. Having no fatal engineering flaws. The study found no fatal flaws in the project design, opening the way for additional study.

The Los Angeles – San Diego – San Luis Obispo (LOSSAN) Corridor is the second busiest intercity rail corridor in North America.

The feasibility study is a result of a legal settlement between Caltrans and the CNFF. CNFF had challenged Caltrans’ approval in 2013 of plans to widen the I-5 Freeway from La Jolla to Oceanside in San Diego County. CNFF’s litigation goal was to identify alternatives to carpool lanes that would further decrease vehicle miles traveled (VMT) and greenhouse gas emissions in the region.

In mid-2020, SANDAG will commission the San Diego Regional Rail Alternatives Study, which will build upon the Miramar Hill improvements outlined in this study, as well as explore ways to improving rail service and operations of the entire LOSSAN corridor from the Orange County line to Santa Fe Station in downtown San Diego.