Connecticut Department of Transportation, with the support of the Transportation Strategy Board, is preparing an environmental assessment for commuter rail service between New Haven and Hartford, Connecticut, and Springfield, Massachusetts. The study area corridor is 62 mi of existing rail line, which is owned and operated by Amtrak. This rail corridor line is commonly referred to as the Springfield Line. Besides a regional passenger service, four freight carriers use the line: Connecticut Southern, Pan Am Railways, CSX Corporation, and Providence and Worcester Railroad. A limited section of double track and long freight dwellings along the main line both demanded multiple alternatives to be analyzed according to capacity improvements and operational changes. Analysis was conducted by means of the Rail Traffic Controller software. The commuter plan was analyzed under two main scenarios: a start-up near-term service (Year 2015) and a future service (Year 2030). The outer year testing also included an iteration of improvements given implementation of high-speed rail on the line. The purpose of this discussion is to identify the track capacity and operational requirements for an efficient integration of freight, Amtrak, commuter, and high-speed rail service.