Speeding up the greenline

[octr202]

You got it -- why I didn't consult the online MBTA equipment Bible first is beyond me. Blue Line cars are 111" wide. On a side note, that makes them far too narrow for shared trackage with the Red Line (which is 122" or 120" depending on car).

[jwhite07]

Right... 111" is the maximum width, but it's not the width over the door thresholds. Even though the door thresholds do stick out a few inches from the frame at floor level, the carbody cants slightly outward from the frame up to just below the windows and then back inward to the roof. So the maximum overall width of 111" actually is reached just below the windows, a couple of feet above the thresholds. And since we're talking about platform clearance, the threshold width is what matters, not the maximum width.

I have an old Rollsign magazine at home that shows the width over door thresholds for the old 0500-series cars... although the 0600s are definitely wider overall than the 0500s were (unlike the 0600s, the 0500s had straight sides), I believe the threshold width remained the same because the 0600s had to use the existing platforms.

[trigonalmayhem]

Speaking of the "urban ring," all the rough plans I've seen seem to be too far into the city. Personally I think they should try duplicating the 66 (at least from the masspike to dudley) with light rail and then maybe run it to central and beyond to inman and then who knows from there.

I never saw the point of their BRT or whatever going in such a tight loop around downtown.

[jwhite07]

Just checked my old Rollsign... the St. Louis-built 0500s from 1951 had a width over thresholds of 103" (the Pullmans from 1924 had a width over thresholds of 102 1/4"). So, depending on where the maximum width of an LRV occurred, they might not clear a Blue Line platform after all!

My bad.

[octr202]

wow -- I had no idea there was that big a difference. Oh well, even if they fit there'd end up being a whole host of reasons why it couldn't be done...it just wouldn't seem right if it was too easy.

[vanshnookenraggen]

A big question, though, if you run the Blue Line from Govt. Ctr. to Kenmore, north of the Green Line, is how do you connect to the Red Line. It would be a shame to start this project and miss this connection. Creating a Park St. Even Further Under would be great from a connectivity standpoint, but would require totally redoing the Blue Line at GC (or eliminating it -- you would still have a GL connection at Park St.). The other option is to go up to Charles MGH, and then take a hard left and go down Charles St. to about Beacon St. and then head west. Regardless, it'd be pretty tough to do.

If the Blue Line cars weren't so small, you could perhaps create a junction with the Red Line under Beacon Hill, run them thru Charles and Kendall, and then split off into a new tunnel towards Kenmore -- but even with fully compatible equipment, this is really up there with something beyond Big Dig complexity...

Easy, the line would still go to Charles but right before it got there start to curve southwest. Then it would follow Storrow Dr to Beacon St to Kenmore. Simple.

[efin98]

Easy, the line would still go to Charles but right before it got there start to curve southwest. Then it would follow Storrow Dr to Beacon St to Kenmore. Simple.

That routing alone would kill any hopes of that project every getting past the drawing board.

[octr202]

Sadly, I think the chances of ANY tunnel ever getting built under Beacon Hill, whether its the Red Blue connector, a Blue Line extension, new Green Line tunnels, or even the fanicful PMT vision of a Silver Line, is remote at best. The cost would be high -- we're probably talking about costs as higher or higher than the Big Dig (on a per square foot of tunnel area basis -- maybe not in total), plus digging under some of the most historic and expensive eal estate in the metro area. Not to mention that a lot of that land in the Back Bay isn't necessarily the most stable solid ground around either.

At the very least it would take a radical change in the political leadership, at the local, state and federal level, that would make transit projects more of a priority than they are right now.

[Ron Newman]

Extending the Blue Line to Charles Under wouldn't require digging under anyone's property, as it would be directly under Cambridge Street. You wouldn't have to do any deep boring either, just cut-and-cover. This is all solid ground, too, not landfill.

[efin98]

Extending the Blue Line to Charles Under wouldn't require digging under anyone's property, as it would be directly under Cambridge Street. You wouldn't have to do any deep boring either, just cut-and-cover. This is all solid ground, too, not landfill.

Even if no property is affected any construction would require the closure of the street and or the reroute of traffic to other streets in the area. that alone would not sit well with the residents of Beacon Hill and the West End.

[octr202]

In a lot of places, deep bore is probably preferable in the city -- less surface disruption. I can't see many people being happy with a curb to curb excavation of Charles St. (especially after the reconstruction now) for a long time to come.

[Cotuit]

Isn't there a partially built tunnel under Cambridge Street? Does anyone know how far it extends? Cambridge Street wouldn't have to be completely dug up from Bowdoin to Charles for a cut-and-cover line would it?

If the line were to be extended from Charles to Kenmore via Storrow Drive, the best tunneling means would probably be deep bore (for soil conditions, the nightmare cost of shutting down Storrow Drive for cut-and-cover, and that any blue line at Kenmore would need to go below the existing tracks).

Looking at the Big Dig, it doesn't seem to be beyond the bounds of engineering to be able to keep traffic running on Cambridge Street for the surface work that would be required to connect the existing tunnel to a new deep bore.

Of course it would cost a lot, what new subway line doesn't? A cost benefit analysis would need to determine how many riders would be taken out of the green line and how much improvement in green line flow we would see. And the switch at Copley needs to be addressed to see the most improvement in green line flow.

[octr202]

Speaking of things like the Copley switch that slow the Green Line down, just how many safety stops are there in the tunnel? I know that there is one between Hynes and Kenmore -- this one in particular seems to take a long time to clear -- like 4 to 5 seconds. There also seems to be another one approaching Arlington (outbound at least -- can't remember if there's one inbound). Are there others?

Also, the Green Line's switch control essentially requires cars to approach all switches at slow speed and pause before them, correct? I am under the impression that this is because they are controlled by some sort of transponder/reader setup that reads the line code for whatever route they are running. This seems to add a good bit of additional time too.

The gist of all of this is, then, that wouldn't the single best investment for the Green Line be a new signal system? Ultimately a system with cab signalling, ATC (or ATS, ACSES, anything that can enfore a stop indication), and perhaps a moving block system like San Francisco tried would provide the best benefit. If the T is considering this, then they are making a wise descision to wait until other cities work some of the bugs out of it -- I know SF's Muni has had trouble with their new system. In time, however, there should be good options along these lines available.

[efin98]

In a lot of places, deep bore is probably preferable in the city -- less surface disruption. I can't see many people being happy with a curb to curb excavation of Charles St. (especially after the reconstruction now) for a long time to come.

They would deal with it for a bit as it's only for the section between the end of the current storage tunnel and Charlse Circle that could handle cut and cover construction. After Charles Circle anything built would have to be deep due to the Back Bay.