The Atchison, Topeka and Santa Fe Railway's main contribution to BNSF was the Southern Transcon, a fast intermodal corridor connecting Southern California and Chicago. Most traffic is either trailers of trucking companies such as intermodal partner J. B. Hunt, or containers from the Ports of Long Beach and Los Angeles. The latter begins its trip on the triple-track Alameda Corridor, shared with the Union Pacific Railroad, and then follows BNSF rails from downtown Los Angeles. Its route, the Southern Transcon, has been almost completely double-tracked, and triple-tracking has begun in areas such as Cajon Pass.