Given that consensus is that we need to increase capacity on the Old Colony lines and that it will be incredibly expensive to double track through Quincy and JFK, I wanted to bring back up an idea that got thoroughly shut down on this board when it was brought up a while ago - removing the Braintree branch from the Red Line and converting those stations to serve shorter BEMU/EMU trainsets while maintaining longer express platforms at Braintree and Quincy Center.
My main assumption with bringing this up again are that it will cost much less to reconfigure 5 platforms + track integrations compared to redoing a significant amount of 3 stations + widening the ROW underneath Burgin Pkwy and in other spots.
When I look at all the " blowing up" that will have to happen, as well as images like the one below, all I can think is that will be a nightmare in cost and disruption to get through. It makes me start to think that the slightly longer frequencies in Quincy + extra transfer with frequent and relatively easy transfer at JFK to get further than South Station+ better frequencies to Ashmont through Savin Hill is worth it. This way you are triple tracking one line rather than double tracking two separate ones in the same ROW. Each way you are increasing service to Brockton and the South Shore and (I think) will require either SSX or NSRL for additional capacity.
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I know that there are other unique differences that would add to the cost of converting the entire ROW to regional rail like slopes on flyovers, are those going to be as much as a cost barrier? Addiitonally, f
rom the posts I could find in 2016, the reason why it's a terrible idea were
1- Frequencies will at best be 15 minutes and always inferior to RL (by 1-6 minutes depending on time of day) due to terminal district, FRA rules, and dispatching.
2- Disruptions to commuting destinations by losing 1SR from Quincy to Park St, MGH, and Cambridge.
I'm not knowledgeable enough about the interlocking to try to assert a 10 frequency claim from 2tph on each of the 3 branches, but I don't think the additional transfer for Cambridge and MGH is insurmountable. I'm well aware we don't want to downgrade service at all, but if the goal is giving South Shore and Brockton a major upgrade to service/ realistic transit option, wouldn't this slight downgrade to Quincy be the easiest/most affordable way?