A MARC train leaves Union Station bound for Baltimore. (Sarah L. Voisin/THE WASHINGTON POST)

The three new tracks, which are scheduled to open by 2014, will hold Maryland Area Regional Commuter (MARC) trains stored at the station during mid-day layovers, according to the Maryland Transit Administration.

Passengers now endure delays, uncertainty and sometimes long walks to trains because MARC trains are stored on Union Station tracks that also accommodate Amtrak trains, the MTA said. The new tracks, which will be built along New York Avenue near Amtrak’s Ivy City yard east of the station, will store only MARC trains.

Union Station is MARC’s busiest, with 15,000 daily riders, the MTA said.