I'm not sure if the current bridge surface is narrower than when the railroad was running on it. The New Haven Railroad moved the track arrangement to overlapping in the 1920's I read to center the weight on the bridge because of the increased weight the locomotives it was getting then.
A point of information, the railroad station in the view looking down from the bridge is owned by the New York MTA and is operated by The Metro-North Railroad. Amtrak is a tenant at this station.
Ed G. (Along The New Haven Line of Metro-North and Amtrak, the busiest railroad line
in the U.S.A.)