The LOSSAN corridor is one of the most travelled Amtrak routes outside of the Northeast Corridor. However, to get it to remotely the standards seen on the Northeast Corridor, a lot of improvements would have to be made. These improvements include dual-tracking (at minimum), grade separation to eliminate all grade crossings, and electrification. Phase 1 (Los Angeles-San Diego): This is where much of the ridership comes from so I expect this is where the rebuilding will first take place. Miramar Hill Tunnel: At La Jolla, the tracks take a u-shaped turn to run around Miramar Hill, so a tunnel will be built to cross Miramar Hill. This includes a new station at UC San Diego. Track relocation from Del Mar to La Jolla: At Del Mar, the tracks run dangerously close to the coast line, and at La Jolla, they go through a hairpin turn, so the tracks will be relocated. San Diego freight bypass: This would reroute freight radiating from the San Diego area to follow Interstate 15 and Interstate 215 into Riverside, redirecting freight traffic radiating from the San Diego area, and also making the LOSSAN tracks between Fullerton and San Diego virtually freight-free. This can work as a public-private partnership with BNSF similar to Norfolk Southern's Heartland Corridor. San Juan Capistrano Tunnel: At near Dana Point, there is a near 90 degree turn, which will hamper speeds. A new tunnel between San Clemente and San Juan Capistrano will have to be built. New ROW between Santa Ana and LA Union Station. Amtrak California can acquire the lightly-used Anaheim Subdivision from Union Pacific between Santa Ana and Norwalk and redevelop the ROW. Between Norwalk and Commerce, a new ROW following Interstate 5 will be built (can certainly make better use of that widening they've been doing), and between Norwalk and the Redondo Junction Grade Separation, a new elevated ROW will be built following the existing ROW. The Redondo Junction will be quad-tracked and connect only to the new Anaheim rail line. This will eliminate any track-sharing with freight trains. In tandem with the Norwalk-Fullerton rebuild, two tracks will diverge to run on the BNSF line to Fullerton. Norwalk-Fullerton rebuild: between Norwalk and Fullerton, Metrolink and Amtrak run on tracks owned by BNSF. These tracks also run on the Southern Transcon, one of BNSF's busiest freight routes. SCRRA and BNSF can come to an agreement to jointly-own the tracks between Norwalk and Fullerton. Considering that CAHSR has plans to run HSR trains between LA and Anaheim using this route, SCRRA and BNSF can work with each other on eleminating all grade crossings and quad-tracking the entire line. This is similar to what CAHSR has planned for its LA-Anaheim route. New maintenance facility: Amtrak has an existing maintenance facility (8th. Street Yard). While it's currenly fine as it, should the LOSSAN line and its radiating lines be modernized, the rail yard would be insufficient to handle the increased frequencies (this issue would also likely plague Metrolink). A reactivated Taylor Yard could have happened but G2 (where the majority of it is) has been earmarked for redevelopment as a residential community. This would make finding space for a new maintenance facility extremely difficult. A new maintenance facility in Commerce would be impractical as it's too far out from LA Union Station. The closest would be the existing ex-SP rail yard, but Amtrak and the SCRRA would have to negotiate with UPRR to gain a piece of it to remake it into a new maintenance facility. Such a development can happen best in tandem with a new route following I-10 via a redeveloped El Monte Busway. Phase 1.5 (Salinas-San Jose): Amtrak is planning on extending Capitol Corridor services to Salinas. Modernization and improvement of this route can happen in tandem with the Los Angeles-San Siego modernization. Salinas Direct: This rail line closely follows US Route 101, bypassing Watsonville and Castroville, as well as several wildlife preserves. New Gilroy-Salinas via Castroville and Watsonville alignment: The existing ROW runs sandwiched between wildlife preserves. This realignment will have the tracks run in parallel with CA-1. To bypass a granite mine, the realignment will tunnel south of Aromas to connect with the Salinas Direct. Phase 2 (Los Angeles-San Luis Obispo): Compared to the Los Angeles-San Diego, this section will be more difficult to build as there will be a lot more ROW acquisitions as the existing route is too winding for even a modern higher (i.e. 125 mph) speed rail line (particularly on the ROW that parallels UP's Coast Line as UP is clingy with their tracks but I can see them benefit from a rebuilt and modernized rail line) New Los Angeles-Camarillo rail line: Between Camarillo and Los Angeles, a new rail line will be built, largely parallelling US Route 101. Much of this new rail line will be either elevated (such as through Ventura Boulevard) or underground (such as from LA Union Station-Studio City and much of the Conejo Valley). Upon being built, all Amtrak and Metrolink services will relocate to the new line. This would end up supplanting Metrolink services through the Simi Valley, so a DMU will be used for the old Ventura County line. New Gaviota-San Luis Obispo track: Similar to the new Camarillo-Los Angeles track, a new ROW will be built paralleling US Route 101. This will bypass Lompoc and Vandenberg AFB and enable Amtrak to serve Santa Maria Phase 3 (San Luis Obispo-Salinas): This section has no corridor service, being only served by the long-distance Coast Starlight. Currently along this section, Amtrak plans to add stops to Soledad and King City. This section will likely be the last to be completed in the modernization program. Cuesta Base Tunnel: The existing route has a very long and winding segment north of San Luis Obispo as it asends the Cuesta Pass. Building a new tunnel will shave off a sizeable portion of time.