What is the track on the side of the convention center used for and what was it originally used for
The convention center property used to be a New Haven freight yard. The track connected to New Haven main at South Bay (near present T Cabot Yard)
Southwest of Cypher St. it is MBTA red line test track. Lots of discussion here----https://www.railroad.net/plan-to-use-tr ... 65430.html