I appreciate the desire to serve the largest population center between Quincy and Providence/Fall River/ New Bedford, especially compared to the much smaller cities and towns surrounding it. However, it seems a lot better value on the whole to increase Brockton service through CR rather than trying to extend further the longest end of an already branched line.You don’t have to eliminate any CR lines, the target goal is to increase frequency to Brockton specifically. Beyond that frequency for the CR can be hourly. Does anyone know what the capacity of the OC line is from Braintree-SS? Bi-directional All day hourly frequency for the other 2 lines may be doable. That’s only 6 TPH in the single-track sections.
The cost would be massive to grade separate, build stations, and widen the ROW to accommodate triple tracking (with stations). All that to serve one destination every 9-13 minutes on a much longer trip to Boston. Compare that to the cost of double tracking Braintree to Montello, a turnback track after Campello for short turns, and focusing your money on double tracking through Quincy. This way you improve the frequency/experience for the entire South shore and the short turn could get you to 15-20 minute frequency on a faster trip to the city. As we move closer to battery/electric regional rail, the advantages of heavy rail subway are lessened but expansions will cost a lot more. If they don't bring system wide improvements (like Orange to Reading and sending Haverhill trains via wildcat branch), I think it's pretty hard to argue for their value as a straight swap.