Tobin Bridge Relocation/Replacement

[F-Line to Dudley]

I return to the question I raised earlier, would rail on a draw (lift) span under the highway span be unbearable? How often is the 135ft. clearance needed? Would needing to open the span occasionally really be that disruptive to transit performance?

Daily Chelsea St. bridge raisings are disruptive to SL3's schedule, so probably. Plus you'd make the bridge more than a billion dollars more expensive by adding a third deck, and a movable one at that. And the fact that you'd still have to maintain 135 foot maximum clearance means that the highway decks would have to be even higher to tuck a raised rail lift underneath them in the open position.

 

[JeffDowntown]

Daily Chelsea St. bridge raisings are disruptive to SL3's schedule, so probably. Plus you'd make the bridge more than a billion dollars more expensive by adding a third deck, and a movable one at that. And the fact that you'd still have to maintain 135 foot maximum clearance means that the highway decks would have to be even higher to tuck a raised rail lift underneath them in the open position.

Perhaps there should be a serious public policy debate about whether a high bridge is even warranted there. Isn't the only shipping destination remaining between the Tobin and the Earhart Dam the auto terminal. How much are we going to spend to keep the auto terminal there? I don't believe there are any other port facilities left in the Mystic basin (certainly not frequent users). (And yes, I know Federal law makes taking a waterway out of navigable service very, very difficult. Is it $ Billion difficult?)

 

[F-Line to Dudley]

Perhaps there should be a serious public policy debate about whether a high bridge is even warranted there. Isn't the only shipping destination remaining between the Tobin and the Earhart Dam the auto terminal. How much are we going to spend to keep the auto terminal there? I don't believe there are any other port facilities left in the Mystic basin (certainly not frequent users). (And yes, I know Federal law makes taking a waterway out of navigable service very, very difficult. Is it $ Billion difficult?)

Do you want to gander on an incredibly long-term dysfunctional federal government even paying mind to bureaucratically changing the clearance for one isolated case on somewhat invented cost control grounds for a transit line that hasn't even been subject to a single feasibility study yet? Incredibly unlikely that they budge on any sort of timeframe that allows us to navel-gaze at concepts for Tobin II before Tobin I's maintainability starts becoming a bad year-to-year cost issue. Look at how analysis paralysis has functionally turfed a vastly simpler rebuild project in Allston. Tobin II is a devastatingly difficult prospect to begin with with all its moving parts. If it's going to be extremely more physically, bureaucratically, and existentially complicated the chances rise terrifyingly high that we simply get nothing done.

The feds could always just decree that if we want the transit line so badly we just pick a different alignment or do a tunnel or do a sealed BRT or rubber-tyre metro line in a separated lane on the stet grades. Nothing's requiring us to do a Tobin alignment in the first place when there are multiple ways of getting a branch or new line to Chelsea/Everett. Again...there's no feasibility study whatsoever yet, so we can't so much as speculate that the ridership will completely crater if the alignment has to come out of Somerville or Revere at slightly longer travel time instead of going straight up the gut of the Navy Yard and Tobin. This so far is just an odd, incomplete, and somewhat out-of-character TransitMatters crayon fascination with ensuing Internet argument...not a real proposal backed by any shred of study evidence. Meanwhile, the new bridge needs to start showing soonish design starts if we're ever going to mount the enormity of the replacement project on a time frame that won't murder the actual costs.

 

[JeffDowntown]

Do you want to gander on an incredibly long-term dysfunctional federal government even paying mind to bureaucratically changing the clearance for one isolated case on somewhat invented cost control grounds for a transit line that hasn't even been subject to a single feasibility study yet? Incredibly unlikely that they budge on any sort of timeframe that allows us to navel-gaze at concepts for Tobin II before Tobin I's maintainability starts becoming a bad year-to-year cost issue. Look at how analysis paralysis has functionally turfed a vastly simpler rebuild project in Allston. Tobin II is a devastatingly difficult prospect to begin with with all its moving parts. If it's going to be extremely more physically, bureaucratically, and existentially complicated the chances rise terrifyingly high that we simply get nothing done.

The feds could always just decree that if we want the transit line so badly we just pick a different alignment or do a tunnel or do a sealed BRT or rubber-tyre metro line in a separated lane on the stet grades. Nothing's requiring us to do a Tobin alignment in the first place when there are multiple ways of getting a branch or new line to Chelsea/Everett. Again...there's no feasibility study whatsoever yet, so we can't so much as speculate that the ridership will completely crater if the alignment has to come out of Somerville or Revere at slightly longer travel time instead of going straight up the gut of the Navy Yard and Tobin. This so far is just an odd, incomplete, and somewhat out-of-character TransitMatters crayon fascination with ensuing Internet argument...not a real proposal backed by any shred of study evidence. Meanwhile, the new bridge needs to start showing soonish design starts if we're ever going to mount the enormity of the replacement project on a time frame that won't murder the actual costs.

I get it, but this is an great example of horrible cost-benefit analysis. Even the highway bridge alone is much cheaper if it does not need a 135 ft. clearance that virtually no one is using.

We are insisting on keeping the 135 ft. clearance because ..... reasons.

 

[Riverside]

The specific issue is steel-wheel braking performance on slippery rail, which is a function of how many axles and how much weight the train has. The feds go with generic reference cases for their recommended standards, the T goes with its actual maximum car counts running empty consists but never exceeds the fed guidelines. It's not an easy thing to reengineer around, because it's extremely invasive to add more axles to rolling stock (with massive downsides in increased power output, maintenance complexity, rougher ride, and much-increased wear on the track). The reason rubber-tyre metros can take almost double the grades is because rubber has lots more friction than steel on a surface, and those trains have many more axles than steel-wheel trains to better distribute the weight on air-filled tires.

This is going to be a very hard blocker to try to engineer around. There likely aren't vehicle-side solutions you can deploy, so it all comes down to how the bridge approaches are engineered within the available space and how much more expensive it would be to significantly modify them for gentler grades.

This still doesn't address the bigger question. The apparent need is to reach a height of 135 feet; from the south, starting at ground level at Constitution Road, its about 4,400 feet to the edge of the Mystic -- that would be just over a 3% grade; the north side is a little bit harder to measure, but to Everett Ave, where the lower deck's roadbed is, say, 20 feet elevated, it would be 2,900 feet to descend 115 feet -- that's a 4% grade.

With some adjustments, those grades could even potentially be in Red Line territory, per your figures :

From the T's CRRC vehicle specs, these are the maximum grades for HRT in Boston:

• Red - 4% for up to 1200 ft., less than that is unlimited.
• Orange - 5.6% for up to 60 ft., 4% for up to 750 ft., less than that is unlimited.
• 6% maximum on the vehicle design tolerances for safe braking.

Yeah...it's a pretty large discrepancy vs. the current Tobin approaches.

EDIT: If Tobin II is going to have similar grades, you'd almost have to consider a rubber-tyre metro, which is functionally a form of HRT (it has third rail and runs in a grooved 'track' with switches). That can take up to 12% grade, and is preferred in cities that do have especially tall above- or underground grades. But it would have to be an isolated line with no possible branching of any existing T rail line, and has disadvantages of much higher maintenance costs, slip problems with ice, and maintenance practices that are generally alien to the T rapid transit division's established rail shops.

So I don't see an immediate justification for all the handwringing. Like I said, I'm not an engineer, so I'm happy to learn the nuances here.

But on the face of it, the math suggests that the grades would be just fine.

 

[Riverside]

I've become convinced that Route 1 really isn't the best alignment. It's the least efficient of the three likely routes (Everett Broadway, Route 1, Revere Broadway) in terms of riders per mile, and it doesn't hit the commercial centers of either Everett or Revere. It doesn't relieve the Everett Broadway buses at all, and it only relieves the Revere Broadway buses at Bellingham Square. You're building a ling through straight residential without hitting any of the nodes.

I largely agree with you. Well, actually, I entirely agree with you that Route 1 isn't the best alignment. But, for completeness' sake, I think it's worth reframing the benefits of a Route 1 alignment, somewhat.

IMO, this actually comes back to the question of the "Lechmere Model" and the "Medford Model". Under the "Medford Model," embodied by GLX, the rapid transit service attempts to serve the neighborhoods directly, without relying on connecting surface transit, and usually employing closer stop spacing. The "Lechmere Model" (which could also more broadly be called the "BERy Model"), uses rapid transit stations as transfer hubs, leveraging surface routes to actually serve neighborhoods directly.

A Lechmere Model along Route 1, combined with a significant rework of the bus network, would be a pretty different situation. (Especially with stations added at Revere Beach Blvd and maybe Sargent St.) A better integrated network of bus routes, operating cross-town perpendicularly to the lines at each station, could be pretty effective. Something vaguely like this:

The one plausible advantage of Route 1 is constructability/cost, but I'm not even sure how much it would benefit. Route 1 is cramped, with no median and not even full center breakdown lanes; there's no room to run alongside like many highway-following lines do. Any elevated structure is going to have to straddle the highway, and be high enough to go over the overhead bridges. That's not going to end up much (if any) cheaper than tunneling.

If you can find a way to relocate automobile traffic off of Route 1 entirely, and just make it a transit ROW...

(Not that I'm advocating for that though.)

 

[Longfellow]

The old freight ROW through Charlestown probably works for this purpose. Here is the 3375 feet it takes to get to 135' at 4% grade. You could even cheat by running the rest of the line down that ROW but then you'd end up in Sullivan.

This all said, if this was ever constructed, it would be one of the coolest heavy rail crossings in the world to ride on, rivaling any in NYC.

 

[vanshnookenraggen]

If you can find a way to relocate automobile traffic off of Route 1 entirely, and just make it a transit ROW...

The curves of the highway make station location very tricky (if not impossible) for ADA platforms, limiting where transit can be effective. Not to mention, it's not like the highway was built to connect walkable areas. It's a terrible ROW for transit, period.

Honestly, the longer I look at this, the more I like bus lanes all the way up Route 1. You can take a lane for BRT/HOV. It's far from perfect, but it helps more of the people who use the bridge along the entire corridor.

If you absolutely must have fixed-rail rapid transit, I don't see it being cost-effective to build it north of Revere Beach Parkway, whatever you chose.

 

[TheRatmeister]

If you absolutely must have fixed-rail rapid transit, I don't see it being cost-effective to build it north of Revere Beach Parkway, whatever you chose.

The stations at Revere Center and Woodlawn are both fairly compelling IMO, and Woodlawn is probably cost-effective because of point 2:

IMO, this actually comes back to the question of the "Lechmere Model" and the "Medford Model". Under the "Medford Model," embodied by GLX, the rapid transit service attempts to serve the neighborhoods directly, without relying on connecting surface transit, and usually employing closer stop spacing. The "Lechmere Model" (which could also more broadly be called the "BERy Model"), uses rapid transit stations as transfer hubs, leveraging surface routes to actually serve neighborhoods directly.

A Lechmere Model along Route 1, combined with a significant rework of the bus network, would be a pretty different situation. (Especially with stations added at Revere Beach Blvd and maybe Sargent St.) A better integrated network of bus routes, operating cross-town perpendicularly to the lines at each station, could be pretty effective. Something vaguely like this:

Along Route 1, both Prattville and Woodlawn are very well situated for bus transfers and integration using the BERy Model. (I like that name better and it's way more fitting, just look at the Washington St elevated stops.) They also have fairly strong walksheds as it is, despite being fairly residential. Prattville is located on the 111, and service along Washington Ave could connect well Everett or Chelsea. Woodlawn is already located on the 110, and is set up for strong connections to Revere Center.

 

[vanshnookenraggen]

The stations at Revere Center and Woodlawn are both fairly compelling IMO, and Woodlawn is probably cost-effective because of point 2:

They aren't cost effective if you have to cut an entirely new ROW through there. By that I mean, via tunnel or viaduct. There is little room for redevelopment until you get to Northgate. Those numbers aren't daily riders, just simply people who live there. Not all of them will be taking the T.

 

[TheRatmeister]

Those numbers aren't daily riders, just simply people who live there

So let's compare with some actual subway stations, plus a couple others on Rt 1.

Station	Walkshed Population	2019 Weekday Boardings (If applicable)	Estimated Riderhship
Bellingham Sq	20.7k		~13.5k (Based on Davis)
Prattville	14.6k		~5k (Based on Revere Beach, some bus transfers added.)
Woodlawn	8.4k		~3k (Based on Revere Beach, some bus transfers added)
Revere Center	10.6k		~3.5k (Based on Revere Beach, some bus transfers added.)
Beachmont	7.1k	3139
Wood Island	7.5k	2102
Revere Beach	10.5k	3098
Davis	16.3k	11442
Green St	12.2k	3055

Revere Beach seems like the closest comparison, with good car connectivity along Rt 1A, although its density is higher. It also likely has very few bus transfers, which makes the math easier. If we use a Residents:Riders ration of 29%, the same as Revere Beach that gives us an estimated ridership for Woodlawn and Revere Center of 2.4k and 3.1k respectively. However, bus transfers would likely push that up to more like 3k and 3.5k respectively.

I could really go either way between Woodlawn and Revere Center. Woodlawn is logistically quite easy. There are no road bridges over Route 1 between Elm St and Revere Beach Pkwy, so it's just a matter of putting up a relatively low height viaduct over Rt 1, then rising up to a station above Elm St. Revere Center is harder, as you'd need to dive into a tunnel for the station under Revere Center. However Revere Center is likely to have higher ridership due to the higher local population, it has a wider variety of land uses, and it would cannibalize an Everett subway much less. In terms of future extension, I'd rate them about equal. Northgate and Wonderland both have potential for redevelopment, with both likely to present some extra challenges.