I will check out his stuff again. Another option is to use the central artery for another Red Line tunnel, etc. Of course you lose some of the benefits with any of these cost cutting measures.
You lose a lot of the benefits if you sacrifice the Artery to the Red Line in any form. There are basically only two non-insane route options for tunneling through Boston between North Station and South Station; under the Central Artery/O'Neill Tunnel, and under Congress Street. The Congress Street alignment can only support two railroad tracks (I doubt that there'd be room there for more than two tracks on the HRT mode, but you wouldn't be looking to build more than two anyway). The Artery can fit four railroad tracks. In all probability you've got room for six tracks and no more, and the choice is what they are and where. Splitting the NSRL between Congress and the Artery, as one of the state's proposals did recently in an unusually-blatant attempt to inflate the cost estimates to hell to kill momentum for a project Baker & Co do not want to do, is not sensible. It'd be an ugly kludge with wonky transfers even if it doesn't require (and it might) doubling up some of the CR portals (hello cost blowout). Red, meanwhile, only needs two tracks, and is thus a much more natural fit for a Congress Street alignment to points north while the NSRL gets its full-function four-track build under the highway tunnel. (Sharing the Artery space between modes saves the cost of the Congress alignment at the expense of shafting the NSRL's throughput capacity.) Screwing over a region-transforming project in the NSRL for the much more local concern of the Red Line, especially when Congress is a better option for the RL anyway, does not to me seem like a good idea.
São Paulo Railway Company. See my reply from a few minutes ago.
Thanks for the information. It is apparently indeed possible to operate a hybrid system. Whether the operational drawbacks of a rack system would unduly hamper throughput (thus compromising the NSRL's value proposition) would need to be studied if such a system were in active consideration. Which it won't be, because there's about a snowball's chance in Hell that the feds fund something born that kludgy. Love 'em or hate 'em, the FRA is not exactly known for proactive regulation (to the point of just
disturbingly recently relaxing some of the asinine crashworthiness regulations that made US rail equipment so damn heavy, despite Europe and Japan having long since engineered much better alternatives in crash energy management), meaning you'd have to find some way to get approval for a never-US-tested hybrid rack-adhesion locomotive with sufficient power to handle anything Amtrak (or the MBTA) cared to throw at it as well as some kind of system to ensure that the trains didn't runaway down those steep, steep grades. If it requires equipment on the cars, bzzt, game over, no sale, Amtrak will not accept a tunnel their NEC fleet can't use, and the feds will accordingly decline to fund it, meaning no tunnel.
I know I sound like a broken record dumping buckets of disappointment on proposals here, but this isn't Crazy Transit Pitches. The NSRL, if and when it is built, will have to be part of the national railroad network, and it will have to have federal funding involved to get it built at all. That means that Amtrak, the FRA, and the entire alphabet soup of Washington get to have a huge say in its design and construction whether we like it or not. And thus far I've seen nothing at all to answer the question of why these parties would voluntarily accept significant design innovations and the ensuing risks, along with permanent operational restrictions, to save on some tunneling. Washington, sadly, tends to lack the imagination even to consider it, though I don't think it makes sense for this project at all.