EMU (commuter type) for subways?

[BostonUrbEx]

Any reason why you can't just use EMUs for subways? Higher speeds for expresses, long distances, etc. Alot more flexibility with three tracks of EMU subway + EMU commuter than just two tracks of subway plus single track commuter.

My guess is the only factor is cost. (And the fact that all our tunnels would need to be widened, but why don't new systems do this?)

 

[Commuting Boston Student]

Any reason why you can't just use EMUs for subways? Higher speeds for expresses, long distances, etc. Alot more flexibility with three tracks of EMU subway + EMU commuter than just two tracks of subway plus single track commuter.

My guess is the only factor is cost. (And the fact that all our tunnels would need to be widened, but why don't new systems do this?)

The start/stop penalty on an EMU is small, but it's still a non-zero value. Rapid transit station spacing is just too tight. That's how I understanf it anyway.

 

[AmericanFolkLegend]

There's not enough Emu's in the US to handle our transit needs. Sure we could bring some in from Australia, but who is going to domesticate them. And if you think subway tunnels are gross now, wait till their filled with guano. The idea is a non-starter.

 

[Nexis4jersey]

It wouldn't work in Boston but could work in DC and Baltimore along with LA and SF due to spacing by greater...

 

[F-Line to Dudley]

The start/stop penalty on an EMU is small, but it's still a non-zero value. Rapid transit station spacing is just too tight. That's how I understanf it anyway.

Yes...one's built for short-distance acceleration and a low top speed. Red Line cars have a 60 MPH top speed, but can hit that top speed faster than a truck on the road. Metro North M8's have a 90 MPH top speed, but even at more nimble than a locomotive still take a mile or more to hit top speed. One weighs half the other because faster acceleration values lighter frame; one weighs twice the other because faster top speed requires much heavier traction motors supported by much heavier frame (true even with foreign EMU makes that don't have the extra FRA buff strength calories). One can climb steeper inclines to get in and out of subways and up and down Els, and take tighter curves closer to top speed...but has to be grade-separated because the light carbody isn't safe enough for grade crossings. One can't climb >3° incline without slowing almost to a halt and has a substantial speed penalty around curves, but is completely and totally safe to blast through all manner of grade crossings. One cannot run on single track at full speed and full service because the collision risk with a tincan carbody is too great. One is equally adept at any number of tracks, but must pay the weight and acceleration penalty for proper buff strength.


Completely different purposes make for completely different modes. There's no cost savings or additional flexibility to be had by standardizing equipment. One mode is designed for this thing, the other for that thing.

And, really, the only places where this is a dilemma is a rapid transit system built entirely on railroad ROW's where the station spacing is somewhere between, say, BART and the New Haven Line. Even the decision to build BART as rapid transit was a no-brainer because of the quantity of El-running track and inclines.

 

[Matthew]

See Tokyo. Commuter trains use the subway.

The reason we can't have that kind of sharing here is due to the FRA. They believe in hocus pocus ideas such as extra weight being added to all trains, even though their own studies prove that this makes safety worse. That extra weight makes subway-style operation much more difficult if not impossible.

 

[F-Line to Dudley]

See Tokyo. Commuter trains use the subway.

The reason we can't have that kind of sharing here is due to the FRA. They believe in hocus pocus ideas such as extra weight being added to all trains, even though their own studies prove that this makes safety worse. That extra weight makes subway-style operation much more difficult if not impossible.

No. Euro and Japanese EMU's are considerably heavier than rapid transit cars. Tokyo's setup is explicitly designed for intermixing like that. It's a specific application for their specific need.

Like I said, even Euro or Asian EMU's wouldn't even work on a 'tweener system like BART because of the El inclines and would absolutely maim the schedule management with the poorer start/stop performance. They are wholly, fundamentally different vehicles. And rapid transit isn't governed by the FRA, so there's nothing preventing them from being used on closed systems. If it's disconnected from the national RR network they can run whatever rolling stock they want. Or get an FRA waiver like PATH, Staten Island Railway, and NJ Transit River Line where there was or still is a physical connection to the network and service hours are wholly time-separated from RR traffic. RT vs. RR is a wholly voluntary choice, not the result of punitive regs crammed down people's throats.

Know why NYC replaced all the steam trains on its Els with rapid transit at turn of the 20th century and never went back when EMU's got perfected? Because RR equipment on the Els sucked ass for moving people efficiently around NYC and rapid transit tincans were great at it. Tokyo's hybrid system is set up that way because EMU hybridization was the best mode. Different modes for different purposes. Pick the best mode for the purpose at hand. Is that really so hard to grasp? Really...this standardization fetish has clear and wholly logical limits when one-size-fits-all requires degrading the service to uselessness. Bureaucracy or no bureaucracy these systems do choose their modes for a reason, and there is a damn good reason why 95% of the time the EMU mode doesn't even make the cut on the initial scoping study for serious rapid transit proposals.