MAX Red Line

The MAX Red Line is a light rail service in Portland, Oregon, United States, operated by TriMet as part of the MAX Light Rail system. An airport rail link, it connects Beaverton, Portland City Center and Northeast Portland to Portland International Airport. The Red Line serves 26 stations; it interlines with the Blue Line and partially with the Green Line from Beaverton Transit Center to Gateway/Northeast 99th Avenue Transit Center and then branches off to Portland Airport station. The Red Line carried an average 10,310 passengers per weekday in September 2021, the second-busiest after the Blue Line. Service runs for 22 hours per day with headways of up to 15 minutes.

Plans for light rail service to Portland International Airport surfaced in the 1980s, and efforts were accelerated during the airport's expansion in the 1990s. The Airport MAX project was conceived from an unsolicited proposal by Bechtel in 1997, and it was designed and built under a public–private partnership between a consortium of Bechtel and Trammell Crow, the Port of Portland, and local governments. Construction of the four-station, 5.5-mile (8.9 km) branch line began in 1999 and was completed in under two years due to the use of local and private financing and existing public right-of-way.

The Red Line began operating between the airport and downtown Portland on September 10, 2001. It was extended west along existing MAX tracks to Beaverton Transit Center in 2003. Track improvements as part of the A Better Red project are scheduled for completion in 2024; this project adds a second track to single-track segments along the Airport MAX and extends Red Line service farther west to Fair Complex/Hillsboro Airport station in Hillsboro.