from Bakersfield continue west to Oakland, while two trains proceed north to the state capital of Sacramento. Central Valley communities served include Fresno, Corcoran, Hanford, Lodi, Madera, Merced, Modesto, Turlock/Denair and Wasco. Delta/Bay communities of Antioch, Martinez, and Richmond are also served by the San Joaquin. Los Angeles is not served on this route due to the bottleneck of the Tehachapi Pass line, where the Union Pacific prohibits passenger train use due to freight traffic along the world's busiest single-track railway. (On rare occasions Amtrak trains use this as a detour if their railway tracks are being repaired.) The San Joaquin has operated since 1974. Capitol Corridor The Capitol Corridor route, operating since 1991, runs north from San Jose through the East Bay to Oakland and Richmond, then east through the Delta communities of Martinez and Suisun City, and the Sacramento Valley cities of Davis and Sacramento. One Capitol Corridor train per day continues east of Sacramento during the afternoon commute to the small Sierra Nevada town of Auburn, returning in the morning. It is the fourth-busiest Amtrak route nationwide. Rolling stock Locomotives Amtrak California operates a fleet of EMD F59PHI, GE Dash 8-32BWH and Siemens Charger locomotives that are used on San Joaquin and Capitol Corridor trains. These locomotives are owned by Caltrans and carry the CDTX reporting marks. Locomotives from Amtrak's national fleet such as P42DC are often used as substitutes when the Amtrak California dedicated fleet of locomotives undergoes maintenance. Twenty-two additional locomotives built by Siemens will join Amtrak California's locomotive fleet starting from 2017. These locomotives, named Charger, were parts of a multi-state order funded by a combination of federal and state money. Illinois Department of Transportation, acting as the leading agency, awarded the order to Siemens on December 18, 2013. Caltrans ordered the first six with the initial order in 2013, then exercised the option to buy 14 more locomotives in 2015 to replace Amtrak-owned locomotives currently used on Pacific Surfliner. Two additional locomotives were ordered in 2016. Passenger cars California Car / Surfliner bi-level trainsets Amtrak California's routes typically use bi-level, high-capacity passenger cars, dubbed the Surfliner and California Car. All of the California Cars are owned by the California Department of Transportation (Caltrans). Amtrak owns most of the Surfliner cars with some owned by Caltrans. The design of the cars is based on Amtrak's Superliner bi-level passenger cars, but several changes were made