Question, I don't believe I have ever seen this raised in ArchBoston. Why does Boston not consider open gangway trainsets (AKA centipede or accordion trains) to increase capacity on heavy rail transit lines. These trainsets are common in about 3/4 of the subway systems around the world, but not in the US.
Article from Slate:
http://www.slate.com/articles/busin..._gangway_cars_why_does_the_u_s_resist_it.html
You could ask exactly the same for New York, which has overcrowding issues that make open gangways a far more acute need there than here. "We've always done it this way", blah blah blah. The MTA had to be dragged kicking and screaming into *considering* it, but consideration is all they're giving it so far. They have so few options left for easing overcrowding that the vehicles themselves need to start offering a better solution.
Simplest explanation for the T is that the crowding aspect is so low on the Top 10 list of problems to address that it's simply not going to rate very high as a factor for car orders. If an RFP for open gangways is going to thin the herd of bidders just slightly, probably better to just not thin the herd at all this time. Orange's overcrowding is from having too few cars to do the rush hour headways the line is natively capable of; that problem goes away when the new cars substantially increase the fleet size. Red's overcrowding is from inadequate traffic distribution downtown making platform dwells at Park + DTX + SS a schedule drag that's disrupting headways all the way back into Cambridge. That's not really something increased vehicle capacity would do anything to address; modern re-signaling, fixing the constipated egresses at Park/DTX, and getting those all-critical radial subway builds moving are the solutions. Blue going to 6 cars in the last order leaves them under-capacity and another generation of expansion (i.e. Red-Blue + BLX-Lynn) away from filling back up.
Open gangway vehicles do carry with them *some* added maint costs and *some* added debugging time on the cars before a new order is delivered. As well as *some* customization if the line in question has tighter curves than the default tolerances of a vanilla open gangway design. Orange is straight enough that there's probably nothing out of the ordinary there, but Harvard curve? Yes...you'd have to take the due diligence extra testing time to make sure the articulation stands up to the punishment that tight curve inflicts. And since this ongoing order goes with an identical design for both lines on everything except the literal carbody dimensions, the same enclosed articulation design would be used on the Orange cars with similar debugging lead time before they can get waved into service.
Time is something they do not have right now with the Orange and Red orders. If getting the articulation right adds 6 months to the delivery, that could be the difference between an extra winter of mass car shortages in 2019 when uptime is at its diciest-ever on the old cars. Perfectly defensible reason to take a pass on it for the present order.
So while there is some intertia and Not Invented Here in-play, there also isn't a compelling reason to change designs when so many other things trump that on the priorities list. We have justifiable nervousness at the T's wildly hit-or-miss history of going custom with orders. HRT vehicles are about as generic and hardest to screw up as it gets. The 3 different sizes and Blue's roof- + ground -level dual power inputs are such cosmetic differences they don't even constitute real design deviations. So why introduce any surplus-to-requirement features with this particular order that could add time to the delivery?
Next HRT car order I could see it being a standard feature to should shoot for. If only because NYC Subway and PATH at that point will probably have a large enough open gangway fleet that there'll be no fear of ordering the same vanilla stuff in Red/Orange/Blue configurations and risking all that unnecessary extra "Buy America" assembly overhead screwing something up.
But by next order we'll probably have a much larger heavy rail system to feed, as well as fixes of the downtown mobility clogs such that the lines are firing on all cylinders. By that point the capacity advantage of open gangways will be directly addressing a need to control onboard crowding, instead of today being neutral and wholly unrelated to what's causing downtown congestion and what needs to be done to fix it.
