The Alameda Corridor is a 20-mile (32 km) freight rail "expressway"[1] owned by the Alameda Corridor Transportation Authority (reporting mark ATAX) that connects the ports of Los Angeles and Long Beach with the transcontinental mainlines of the BNSF Railway and the Union Pacific Railroad that terminate near downtown Los Angeles, California.

[2] Running largely in a trench below Alameda Street, the corridor was considered one of the region's largest transportation projects when it was constructed in the 1990s and early 2000s.

[4] At the time, cargo traveling by rail to or from the ports could be routed along the Atchison, Topeka and Santa Fe Railway's Harbor Subdivision or the Southern Pacific's tracks down Alameda Street.

The Harbor Subdivision was 90 miles (140 km) long, traveling out to the west side of Los Angeles, before turning back east towards the ports.

Meanwhile, the Southern Pacific route had more than 200 street-level railroad crossings where automobiles had to wait for lengthy freight trains to pass.

[13] The Alameda Corridor–East project was established in 1998 by the San Gabriel Valley Council of Governments to upgrade over 70 miles (110 km) of railroad tracks in the area east of Downtown Los Angeles.