Line 50 is a local route that operates between the City of La Mirada and Downtown Los Angeles primarily via Washington Boulevard. Major destinations include Downtown Los Angeles, Pershing Square, industrial areas in Los Angeles, Vernon, and Commerce, Commerce City Hall, Pico Rivera Town Center, Santa Fe Springs Town Center, Presbyterian Inter-Community Hospital, Whittier Union High School, Whittier College, Whittier City Hall, The Quad at Whittier, Frontier High School, California High School, Biola University, La Mirada City Hall, and La Mirada Town Center. In 2000, MBL assumed this route after LACMTA cancelled contracted service on their Line 105.
Line 50 operates weekday and Saturday service from approximately 4:30 a.m. to 11:15 p.m. Weekday headways are thirty minutes and hourly on Saturday.