|Construction of new platform 7|
This is the first stage of large construction project that will eventually lead to the temporary closure of tracks 3-6 which will be converted to through tracks.
You see, Union Station is a stub station: the tracks are dead ends and all traffic comes from one direction. Trains from the south come in on a long sweeping 180 turn, and then essentially reverse out of the station on the same route (hence the consist has a locomotive at one end, and a cab car at the other, leading to a push-me-pull-you sort of trainset). The plan is to connect several tracks over the 101 freeway and link them to the mainline along the river. That way, through trains from San Diego to Santa Barbara will just keep going, and trains going/coming south won't have to make that long turn into the station.
|Union Station at night|
It's a big project, though, and since those eventual-through tracks will be out of commission for some time, it's essential to increase track capacity. Hence, Platform 7 is being rebuilt. At the rate they are going,I'm not expecting to see through trackage any time soon.