The Metro Green Line is one of the most unusual light rail lines in North America. It uses the same cars with operators and operating characteristics as the Blue and Gold Lines but lacks a single grade crossing, running in the median of the Century Freeway (I-105) for most of its 20 mile length except for about the four most western miles and stations when it curves south in El Segundo running on an concrete ariel guideway. Since the line lacks grade crossings it seems like an automated SkyTrain type people mover like technology would have been more suitable to serve the corridor (and could have been directly integrated with a proposed LAX Airport People Mover to those terminals).

The line has never lived up to its ridership potential (although it narrowly beats out the gold line) and was designed in the 1980s to connect workers to the aerospace industries in El Segundo where it passes through an industrial area. The line opened on August 12, 1995 after the Cold War had ended and in the midst of a population shift around the line with poorer transit dependent residents moving in and replacing the more affluent choice transit (have access to a car) riders along the line. This means that the train serves as a vital transit artery but most of the Park & Ride lots (found at every station except Mariposa) sit extremely empty, some being already slowly reclaimed by nature with cracks developing in the concrete. The fact the train is the only Metro Rail Line that doesn't go into downtown L.A, requiring those passengers to switch to the Blue Line or Silver Line Express Bus along the Harbor Transitway continues to keep Park & Ride ridership low. The lines other flaw is the fact it passes just south of LAX but doesn't enter the Airport at all, passengers must transfer to a slow shuttle bus ride. The eastern terminus at Norwalk, could also be extended less than 3 miles for better regional connectivity to the Norwalk/Santa Fe Springs Metrolink Station.