Metro Red and Purple Line Train Yard; photo by David Mayerhofer/Flickr

‘How do they do that?’ is a new series for The Source that explores the technology that helps keep Metro running and passengers and other commuters moving. Some of it applies directly to the trains, buses and freeways and some of it runs in the background — invisible to nearly everyone but essential to mobility in our region.

How does Metro turn the trains around at Union Station?

Where do the trains come from at Union Station? Is there a departure pattern that those of us who dash from one side of the platform to the other to be first on board don’t understand? At certain times of day the trains pull in, the trains disappear and the trains return. But from where and in what pattern? Is there a roundabout hidden in the tunnel where they turn around?

Trains at Union Station arrive and depart in one of three ways. First, the trains pull out from the Division 20 Red and Purple line rail yard in downtown Los Angeles, near the Fourth Street Bridge and the L.A. River. (More than 100 cars are stored there for the night, as well as maintained and washed there.) They are pulled into the station and begin service from either platform — inbound or outbound — at Union Station. This type of arrival and departure can occur at various times, including when trains are pulling out in the morning or the afternoon.

Second, trains already in service usually arrive and depart from the same platform they arrive on during off-peak hours of early morning, midday and evening.

And third, during rush hour trains already in service pull up to the platforms in Union Station, passengers exit and the trains are swept to confirm that all passengers have exited and no property has been left behind. The trains are then moved to a position just south of Union Station where they can switch tracks (there is no roundabout) and re-enter Union Station on either track — often outbound but not always — for departure.

Trains don’t technically turn around. The train operators simply move from the operator’s cab at one end to the cab on the other to reverse direction.

At any given time there are generally 11 trains (ranging from 2 to 6 cars each) on the Metro Red and Purple lines in and out of Union Station. At the same time on Metro’s 79 miles of rail, there are 24 to 47 additional trains running on the Gold, Blue and Green lines, carrying an average 300,000 weekday boardings.