A Line (Los Angeles Metro)

The A Line (formerly and colloquially the Blue Line) is a light rail line in Los Angeles County, California. Part of the Los Angeles Metro Rail system and operated by Los Angeles Metro, it is the world's longest modern light rail line at 57.6 miles (92.7 km). The A Line serves 48 stations, running east–west between Pomona and Pasadena, then north–south between Pasadena and Long Beach. In Downtown Los Angeles it interlines with the E Line, sharing five stations. Service operates about 19 hours daily with headways as short as 8 minutes during peak hours. It is the busiest light rail route in the system, carrying over 22 million riders in 2024 and averaging 69,216 weekday boardings in May 2024.

The A Line's first segment, between the southern edge of Downtown Los Angeles and Long Beach, opened in 1990 as the inaugural line of the Metro Rail system, using much of the Pacific Electric's former Long Beach Line. Plans to extend the line north through Downtown Los Angeles to Pasadena were proposed in the 1980s but delayed due to funding constraints. Instead, the standalone Gold Line (renamed the L Line in 2020) opened in 2003 from Union Station at the northern edge of Downtown Los Angeles to Pasadena, and was extended east to Azusa in 2016. The original plan was realized with the completion of the Regional Connector tunnel across Downtown Los Angeles in 2023, which linked the A Line to the former L Line. The line was extended further east to Pomona in 2025.