I threw that one in as a crazy transit pitch type of idea, with the emphasis on "crazy". I mean, why not just go with a regular lift bridge instead of this crazy proposal for train elevators on each end of a fixed span. The wait time would probably be similar with either system, and the lift bridge would be a lot simpler.
I'd assume any replacement would need to keep the same height clearance for trucks, so a bridge would likely be easier in that regard. But yes, it could be a tunnel in which case this is a all moot point.
I made the same proposal up thread. A lift bridge for the rail line directly under the Tobin replacement. Keep the rail line down a reasonable level, avoiding the grade issues. I guess the question is what is the ship traffic frequency under the Tobin and how often would the lift need to be open for ships?
Station can be as high up (or as far underground) as needed. There are no fundamental engineering issues. It is all about cost. Every foot above or below ground level adds to the vertical access and construction costs. And there are certain thresholds with step function jumps in cost due to access concerns mandating additional redundancy since walking the stairs is no longer practical for access. And all the vertical access systems also need to be maintained, adding to operational costs.
Because at that level of expense the rail line is going to price out so bonkers that it defeats the whole alignment. Coming out of Somerville or Eastie/Revere or sinking an immersed tube in the river becomes cheaper for serving Chelsea or Everett, and this whole discussion becomes moot because Tobin II is going to flunk handily on cost-benefit vs. the (numerous) alternatives.
I have more thoughts to share in a future blog post, but my belief (at least in principle) is that such a line can and should be turned towards Downtown Boston. Even if it's elevated over the Tobin Bridge.
One option for the Charlestown end for a LRV route on a new Tobin Bridge would be to run the LRV line on the surface alongside City Square, then down the center lanes of the Bill Russell Bridge and North Washington Street, then possibly continuing along the Greenway to South Station. This would avoid expensive tunnel construction in Charlestown and under the River.
Was the Bill Russell Bridge designed for live and static LRV loads, particularly multiple Type 10 cars? LRV bridge loading is a separate and different calculation than for trucks.
This seems solid, assuming the bridge concerns Jeff brought up work out. As long as we're crayoning (which let's be real any new rail line on the Tobin is) what would make the most sense past SS? Roxbury and the Seaport seem like the two options that make the most sense on paper but both are a little redundant with the silver line. Terminating at SS seems like a missed opportunity.
I've had the same LRV loading concern about the Bill Russell Bridge ever since it was first proposed, and brought it up years ago on this forum. MassDOT has historically been really poor at futuring anything they build, and it wouldn't surprise me if this bridge isn't strong enough to support multiple Type 10 cars. Maybe reinforcement of some type could be added to the BR bridge?
This is what I've been stuck on. IMO the clear continuation is Red-X via Cabot Yard. But that would obviously entail modifications to all the stations on whichever RL branch you choose, plus it makes Old-Colony double-tracking harder since you now need to maintain four tracks. through JFK and Savin Hill. With that off the table, the best I can come up with is something along the Washington St axis.
To be fair to MassDOT, given that there's zero current prospect of LRT in Charlestown, no prospect prior to maybe 2050, and not even a conceptual proposal on the table, why would they future-proof for it?
You're right. Funding would not have been available from the Feds or the State to build a bridge hefty enough to handle an LRV line, when that LRV line is not programmed in anything official. I was just wishing.
A multi-use path on the Tobin replacement would be politically mandatory, I would think. The only hangup is the ADA requirements for % grade maximum, plus flat resting spots along the path. What I could find online is a 8.33% grade maximum, but the resting stop requirement was unclear.
I believe if you go on a sustained grade of 5%, there is not a requirement for resting places, but I could be wrong on that.