University of California Transportation Center

In order to alleviate traffic congestion and obtain better air quality in the South Coast Air Basin, the Southern California Regional Rail Authority (SCRRA) began constructing a new commuter train system called Metrolink in October 1992. There are currently five lines in operation: the Riverside Line, San Bernardino Line, Santo Clarita Line, Ventura County Line, and the Fullerton Line. The system is still expanding and when complete, Metrolink will form the nation’s sixth largest commuter rail system, with construction costs exceeding $500 million. Metrolink commuter trains connect suburban communities with centers of business, such as Burbank, Glendale, Industry, and downtown Los Angeles. The SCRRA monitors the passenger ridership counts of each line closely, from which the amount of congestion mitigation can be determined. However, there have been no detailed studies on the direct air quality impact of Metrolink since its inception.