I now have been to one of the second round of public meetings concerning commuter service on the Hartford Line. While the consultants seem to have made quite a bit progress in blending new service in with existing Amtrak runs - cross honoring of tickets being the major point, they still are presenting very pricey alternatives, even with their "minimum build" plan. While I am not an advocate of lengthy, costly studies I do think that a new examinination of incorporating a New Britain-Hartford rail service into this general plan is due, in place of the proposed busway.
When this line was single-tracked, it was about the 3rd or 4th attempt at doing this. While going through records at the former Hartford Trainmaster's office, I found two New Haven RR era proposals - IIRC the years were 1959 and 1967. I Also remember hearing of a Penn Central era proposal to single the line just between Hartford and New Haven, this being around 1970. At any rate, the Amtrak proposal was decided by the late 1980s, and the first trask was to replaced all the stick rail with welded where the track would exist after implementation. This was mainly track 1 (the southbound main). When welded rail began to be installed on track 2, we knew where the passing sidings would be.
One big project not mentioned in much detail in these studies is the rebuilding of the Hartford Station viaduct. When the current Hartford Union Station was built c 1887 (the 1914 date on the building is due to an extensive rebuilding following a fire), a steel trestle carrying four tracks was built to carry the line above street level. Locomotives at the time weighed about 80 tons. Today they weigh over 150 tons, and although the viaduct had been stregnthened a few times over the years, it really needs an extensive rebuild, like many of the bridges of the early 1900s. And it should be rebuilt with the strength needed to fully use the 4 tracks that the structure originally held.
Before the viaduct was reduced to a single track restrictions had been placed on the bridge to prevent more than one train at a time from occupying it. Another problem is that during the 1986-87 rebulding of the station, a building was constructed under the viaduct to house railroad and intercity bus facilities and this building would have to be removed to allow any kind of thorough rebuilding.