Why the extra track and platform at downtown Santa Monica?

[pithecanthropus]

I haven't lived in L.A. for over six years, but I noticed with interest that the western terminus of the Expo Line has an extra track and platform, so instead the usual single island platform with two tracks, there are two island platforms and three tracks". (See picture below.)

Why did they build it like that? Was there some anticipated operational need for the extra track? Given that the maintenance yard is a couple of miles east of there, why would they ever need to accommodate more than two trains at any one time? Moreover, having the extra platform is potentially confusing for passengers, since you need to know which one you're supposed to be standing on when waiting for the train.

It would be wonderful to hear that an express line is being planned, but I'm pretty sure that's impossible.

[bzcat]

The yard is only a mile away but Expo line doesn't run deadhead from the terminus to the yard during most of the service hours. Vast majority of the trains turn back in revenue service at the terminus. The third track at the terminus is for operating efficiency and to provide crush load train and platform capacity during events.

Due to the numerous street crossing on the line, Metro has to anticipate a lot of slack in west bound arrival time so having a spare train ready to depart at the Santa Monica terminus keep the east bound schedule intact and not subject to the delays of west bound operation. In theory you can do that with just two tracks but having three track is easier to stage and keep to the schedule.

The extra platform was designed also to provide enough loading capacity. It allows Metro the use one side of the train to unload and another side to board passengers during really high demand situation. This allows for more holding capacity in the station like when there is an event at the pier or USC football game.

It very easy to tell which platform to go for the next train because usually the train is waiting for you. That's the whole point of having 3 tracks. Occasionally, there may be two trains at the station, in which case, you can tell which one is the next departure because the doors are open for boarding. Also there is the a sign at the front of the platform to show which train departs next. It's pretty intuitive... don't over think it