Metrolink, the marketing name for the Southern California Regional Rail Authority, provides commuter train service on seven routes covering 416 route miles in the greater Los Angeles area: Los Angeles County, Orange County, Riverside County, San Bernardino County, Ventura County, and northern San Diego County. The joint powers authority is governed by representatives of the transit authorities of all the above counties except San Diego County (which runs its own Coaster commuter train service).
The seven routes are as follows:
- San Bernardino Line, San Bernardino to Los Angeles via Rancho Cucamonga, Pomona, and intermediate points: One of the original three Metrolink lines, and the only route with Sunday service.
- Ventura County Line, Oxnard to Los Angeles via Simi Valley, Van Nuys, and intermediate points: One of the original three Metrolink lines, with service supplemented by Amtrak's Pacific Surfliners.
- Antelope Valley Line, Lancaster to Los Angeles via Santa Clarita and intermediate points: One of the original three Metrolink lines; combined with the Ventura County Line between Burbank and Los Angeles. This line was originally named the Santa Clarita Line, originally running only as far as its namesake city, with expansion to Lancaster planned for the future. Then, on January 17, 1994, the Northridge earthquake caused the partial collapse of the interchange between Interstate 5 and California highway 14 south of Santa Clarita, severing the freeway link between Lancaster and Los Angeles. Within a week, Metrolink was providing temporary emergency service beyond Santa Clarita to Lancaster, and the temporary service eventually became permanent.
- Riverside Line, Riverside to Los Angeles via City of Industry and intermediate points: Service on this line began in 1993.
- 91 Line, Riverside to Los Angeles via Fullerton and intermediate points: Using a combination of the Orange County Line and the Inland Empire-Orange County Line (see below), plus a short stretch of connecting track, this line, named for the freeway much of the route parallels, provides an alternate route to the Riverside Line. The line was officially inaugurated on May 6, 2002, although a couple of rush hour trains had been scheduled on the route as early as 1997.
- Orange County Line, Oceanside to Los Angeles via San Juan Capistrano, Santa Ana, Fullerton, and intermediate points: Metrolink service on this line began on December 6, 1993, when the Amtrak Orange County Commuter train, paid for by Orange County, was transferred to Metrolink operation. Full Metrolink service on the line began in March 1994. Service is supplemented by Amtrak's Pacific Surfliners.
- Inland Empire-Orange County Line, San Bernardino to San Juan Capistrano via Riverside, Santa Ana, and intermediate points: Service on this unique line began in 1995, unique because it goes suburb to suburb, unlike every other commuter train route in the United States.
Metrolink's schedules favor the regular morning/evening Monday-Friday commuter, although there is at least one midday train on each line (offering railfans an easy round trip from Los Angeles to the end of the line). The trains themselves are operated by Amtrak employees, with tickets sold by vending machines at every station and checked not by the conductor, but randomly by peace officers with the authority to write a $250 citation.
Metrolink owns its locomotives and bilevel passenger cars (the same lozenge-shaped models used by Ontario's GO Transit and South Florida's Tri-Rail), as well as a portion of its route mileage. The rest of its route mileage is owned by either the Union Pacific or Burlington Northern Santa Fe, which, more than anything else, prevents Metrolink from increasing train frequency on most of its lines, since plenty of freight trains need to use the track, too. In fact, Metrolink occasionally suffers delays due to freight trains, especially on the Riverside Line.
Los Angeles never had commuter train service until Metrolink came along, which is why Los Angeles Union Station is unique among large metropolitan train stations in the United States in that it is now served by more daily trains, by far, than it ever was during the golden age of rail travel.