Complex sentence: The importance of the railroad line for freight traffic diminished with the completion of the Palmdale Cutoff over Cajon Pass in the 1960s, but the route is now used for the Antelope Valley Line of the Metrolink commuter rail system.
Split into simpler sentences: The importance of the railroad line for freight traffic diminished with the completion of the Palmdale Cutoff over Cajon Pass in the 1960s. The route is now used for the Antelope Valley Line of the Metrolink commuter rail system.