what is the point of the 3rd platform in the new rochelle train station?

Answer 1

The two main platforms are for the mainline expresses and some Amtrak trains. The third platform is sometimes used as a local track, but in other instances, is used as the end of the line for trains that finish their runs there, as it is off the main line, and the track rejoins the 4 others just north of the platform, which makes it easier for the small locals to New Rochelle easier to turn around and go back to Grand Central. I hope this has been helpful to you.

Answer 2

local service or if a track is taken out of service for any reason they would use the extra platfomr.