Seaport District to Back Bay DMU Plan

deathtopumpkins wrote:What they need to do is what should have been done to begin with - build the Silver Line as rail. A nice new subway from Back Bay to South Station, then along the Silver Line route along the waterfront, and under the harbor to the airport. That would solve the silver line overcrowding, eliminate the ridiculous route the buses have to take to get into and out of the Ted Williams Tunnel, eliminate the need for dual mode buses entirely, eliminate the need for Massport buses from Back Bay to the Airport, and finally provide a direct rapid transit connection to the airport that does not require a bus ride, or even any transfers at all from Back Bay or downtown.

I agree that the Dudley branch of the Silver Line should have been light rail, which is what the neighborhood activists were expecting when they pressured the T to tear down the el thirty years ago, but as for Logan, I don't think light rail it would currently work in any financially or physically practical way. It would take several large boatloads of money, plus, I assume that you've ridden a Silver Line bus through the tunnel and the airport terminals when traffic is busy, as I have occasion to do every few months. Watch how the drivers have to maneuver their way through the traffic mess. A fixed-route LRV would be unable to change lanes, overtake other vehicles, etc., and thus be slower than the current hermaphodite electrobuses, and there just isn't enough space on the Logan terminal roads to add a dedicated vehicle-free LRV lane at this point. A tunnel under the terminals would be great, but would cost so much that it's even more of a daydream. Maybe it will happen someday, but not anytime soon.

TomNelligan wrote:but as for Logan, I don't think light rail it would currently work in any financially or physically practical way.

Why even bother when there's the Blue Line with the "Airport" stop right nearby. If need be couldn't a loop of some sort be constructed -under or over- the existing maze of roads, etc.?

TomNelligan wrote:

deathtopumpkins wrote:What they need to do is what should have been done to begin with - build the Silver Line as rail. A nice new subway from Back Bay to South Station, then along the Silver Line route along the waterfront, and under the harbor to the airport. That would solve the silver line overcrowding, eliminate the ridiculous route the buses have to take to get into and out of the Ted Williams Tunnel, eliminate the need for dual mode buses entirely, eliminate the need for Massport buses from Back Bay to the Airport, and finally provide a direct rapid transit connection to the airport that does not require a bus ride, or even any transfers at all from Back Bay or downtown.

I agree that the Dudley branch of the Silver Line should have been light rail, which is what the neighborhood activists were expecting when they pressured the T to tear down the el thirty years ago, but as for Logan, I don't think light rail it would currently work in any financially or physically practical way. It would take several large boatloads of money, plus, I assume that you've ridden a Silver Line bus through the tunnel and the airport terminals when traffic is busy, as I have occasion to do every few months. Watch how the drivers have to maneuver their way through the traffic mess. A fixed-route LRV would be unable to change lanes, overtake other vehicles, etc., and thus be slower than the current hermaphodite electrobuses, and there just isn't enough space on the Logan terminal roads to add a dedicated vehicle-free LRV lane at this point. A tunnel under the terminals would be great, but would cost so much that it's even more of a daydream. Maybe it will happen someday, but not anytime soon.

Never once in my post did I say light rail, I said subway. As in heavy rail rapid transit.

As for running LRT through the TWT, as you seem to think I'm proposing: you're absolutely nuts.

Apologies, Mr. Pumpkins, that I misread your post as referring to light rail rather than subway. But yes, I was gently suggesting that light rail to Logan following the current Silver Line route would be nuts.

deathtopumpkins wrote:Never once in my post did I say light rail, I said subway. As in heavy rail rapid transit.

As for running LRT through the TWT, as you seem to think I'm proposing: you're absolutely nuts.

I could also see a fully-automated LRT system with full-high platforms like the London DLR working on a Longwood/Kenmore/Back Bay <-> SS <-> Logan routing, and you could even mix them up with MUNI-style adjustable door height trainsets with automated running in the tunnel for a Dudley <-> SS <-> South Boston streetcar line, if we're going to dream really big.

That would get you the best of both worlds, with cheaper, smaller tunnels that can handle the tight curves of a likely Back Bay -> Boylston/Essex -> SS routing under the existing street plan, but with 90% of the speed and the timetables of rapid transit, with a per-train passenger capacity that's damn close to the Blue Line's. Actually, come to think if it, the DLR is a lot like the Blue Line in that it's a modern re-imagining of a light/heavy rail hybrid. It's a concept that doesn't get nearly enough attention imho.

I thought the idea of BRT was that tracks could be cheaply installed if ridership got too high for trackless-trolleys / dual modes.

tracks could be embedded in the busway and type-8/9 LRVs and existing silver line buses co-mingled. Or high level platforms & red or orange subway cars.

You can't commingle LRVs and trolleybuses under the same catenary - the pantographs would short out the two-wire bus power. You'd have to either give the buses a shoe to run on the tracks, or outfit the LRVs with trolley poles (!).

Trackless Trolley wire does not have to be a specific space apart, nor do both wires have to be the same height. I'm not going to argue that sharing pantographs with trackless trolleys is practical, but it's certainly not impossible. Can't is a 4 letter word.

But given likelihood that future dual-mode bus purchases--and bus purchases period--are going to be battery hybrids the co-mingling problem sort of resolves itself. Real Prius buses...regenerative braking shutting the engine off for stretches of regular service. With that kind of build the bus poles may become just a linear battery charger on a next-gen order instead of the direct-drive traction power. Almost a passive or pass-thru source rather than a real regulation TT when it's in E-mode. And if you wanted to convert the Transitway overhead over to straight-trolley with rails in pavement the buses would keep the engine mostly or entirely off for duration of the tunnel trip and could have their own quick-charging station at the bus loop/layover. Vehicle charging tech will probably be at the point where induction chargers on a plate in the pavement in the bus layover loops on either end of the line can wirelessly quick-charge them and keep in E-mode for the whole duration of an inbound or outbound schedule on SL1. These aren't particularly long or time-consuming routes to cover.

Any which way it evolves, some sort of hybridization--both the tech available today and where it's fast-evolving--can keep engines off in the tunnel enough of the time without needing direct contact with the overhead to free up the 600V DC feed for LRV's to share the tunnel if/when a dedicated connection to the Green Line downtown ever gets built.

CRail wrote:Trackless Trolley wire does not have to be a specific space apart, nor do both wires have to be the same height. I'm not going to argue that sharing pantographs with trackless trolleys is practical, but it's certainly not impossible. Can't is a 4 letter word.

Perhaps one solution could be to split the bus catenary into an overhead and in-ground conductor. Ground the um, ground conductor for safety reasons and have both the trains and bus draw from a standard pantograph. No idea how practical it is, and it limits the bus's freedom of movement, but it's a technically viable solution.

MattW wrote:

CRail wrote:Trackless Trolley wire does not have to be a specific space apart, nor do both wires have to be the same height. I'm not going to argue that sharing pantographs with trackless trolleys is practical, but it's certainly not impossible. Can't is a 4 letter word.

Perhaps one solution could be to split the bus catenary into an overhead and in-ground conductor. Ground the um, ground conductor for safety reasons and have both the trains and bus draw from a standard pantograph. No idea how practical it is, and it limits the bus's freedom of movement, but it's a technically viable solution.

Trackless trolley and light rail already run in harmony in plenty of places. No need to reinvent the wheel, here. Just elevate the trolley wire slightly higher than the catenary wire.

Trackless trolleys and street cars can share the same catenary system even if running in the same tunnel. If they use the same voltage then the positive wire can be centered (and the negative wire off to the right out of reach of the car pantograph). If the voltages are different then the TT wires can be off to the left and right respectively. The same switch hardware (special work) would be used as used in the Green Line joint PCC (pole) and Boeing car (pan) operation, plus movable point frogs at diverging locations. TT poles have no problem following staggered pan overhead.

talltim wrote:The Swiss successfully manage to run EMUs (and powered passenger carrying single cars) with standard coaches and driving cars, and run the same coaches and driving trailers with locos. Its all about having a standard for the wiring.
Having said that, they are moving away from doing so and more towards fixed formation units that can run in multiple.

Sorry if I seem to be "beating a dead horse" here but I was just wondering if a "genset" concept could be applied to DMUs? Possibly even using under carbody rack mounted bays for several modular (removable and swappable) "genset" units per DMU thereby allowing the power to be relatively "tailored" to the need? I envision each "genset" could be slid in and out of the rack mount as desired using something like a forklift in under five minutes, with only one "genset" needed to power the unit and possibly a second coach. Okay, you can laugh now..

papabarn wrote:

talltim wrote:The Swiss successfully manage to run EMUs (and powered passenger carrying single cars) with standard coaches and driving cars, and run the same coaches and driving trailers with locos. Its all about having a standard for the wiring.
Having said that, they are moving away from doing so and more towards fixed formation units that can run in multiple.

Sorry if I seem to be "beating a dead horse" here but I was just wondering if a "genset" concept could be applied to DMUs? Possibly even using under carbody rack mounted bays for several modular (removable and swappable) "genset" units per DMU thereby allowing the power to be relatively "tailored" to the need? I envision each "genset" could be slid in and out of the rack mount as desired using something like a forklift in under five minutes, with only one "genset" needed to power the unit and possibly a second coach. Okay, you can laugh now..

Theoretically, yes. However, it may not be that feasible in the real world. Also, if one could be built, the costs would probably be higher than a normal DMU (which is already going to be expensive), and the benefits are probably not worth the costs. One major benefit of MU's is that the reduncancy is built in, so if a car/pair dies, you still have the rest of the consist to drag it around until it can be shopped. Since the car can be dragged around dead until there is time to repair it, it isn't completely necessary to over-engineer it to allow for slightly quicker repairs.

ns3010 wrote:

papabarn wrote:

talltim wrote:The Swiss successfully manage to run EMUs (and powered passenger carrying single cars) with standard coaches and driving cars, and run the same coaches and driving trailers with locos. Its all about having a standard for the wiring.
Having said that, they are moving away from doing so and more towards fixed formation units that can run in multiple.

Sorry if I seem to be "beating a dead horse" here but I was just wondering if a "genset" concept could be applied to DMUs? Possibly even using under carbody rack mounted bays for several modular (removable and swappable) "genset" units per DMU thereby allowing the power to be relatively "tailored" to the need? I envision each "genset" could be slid in and out of the rack mount as desired using something like a forklift in under five minutes, with only one "genset" needed to power the unit and possibly a second coach. Okay, you can laugh now..

Theoretically, yes. However, it may not be that feasible in the real world. Also, if one could be built, the costs would probably be higher than a normal DMU (which is already going to be expensive), and the benefits are probably not worth the costs. One major benefit of MU's is that the reduncancy is built in, so if a car/pair dies, you still have the rest of the consist to drag it around until it can be shopped. Since the car can be dragged around dead until there is time to repair it, it isn't completely necessary to over-engineer it to allow for slightly quicker repairs.

Agreed, but the point of the "gensets" would be to address the flexibility issue of pulling (or pushing) one or more (as desired) unpowered coaches (or trailers), not "quicker repairs". In an "all DMU" consist, only one "genset" on each DMU would more than suffice.