Loco-hauled metros?

[MattW]

This is more of a devil's advocate "why not" question, but would it make sense to run some metro lines (CTA L, LA Subway, MARTA, etc.) using [electric] locomotive-hauled trainsets instead of EMUs? Right off, I can think of two points against this: bad acceleration, and excessive current draw.

[sipes23]

And diesel smoke in tunnels. I don't know how bad the CTA would be with locomotives where it's elevated, but the blue and red lines would be beyond awful in the underground portions.

[DutchRailnut]

even electric locomotives use less power than entire train of EMU's, that's why their slower.

[mtuandrew]

even electric locomotives use less power than entire train of EMU's, that's why their slower.

Slower to accelerate anyway. And given enough cars and enough distance between stops, it becomes more efficient weight-wise to use a single locomotive to pull a train than it does to use EMUs. That's why Amtrak has invested so heavily in locomotives, and probably why they didn't order more Metroliner-based regional equipment along with Amfleets (that and the price.)

On the other hand, commuter service and heavy rapid transit need redundancy, light weight, and quick acceleration to maintain a tight schedule, and the more standard they can make their infrastructure the better. Locomotives eat up the track as compared to MUs, just like one semi destroys roads much faster than a fleet of pickups carrying the same cargo, and a subway system can't easily take an entire line out of service for repair.

[DutchRailnut]

Amtrak is not running a Metro(suburban) service comparing them to EMU's, is like comparing Ashley Dupre' to Virgin Mary.
EMU's have on average 600 hp per car or more, and because of all wheel drive a hell of lot more acceleration than locomotive with 4 axles.

[electricron]

even electric locomotives use less power than entire train of EMU's, that's why their slower.

Doesn't that really depend upon how long the train is?
I've read that the break even point between diesel locomotives and RDCs is around 4 coach cars, source TRE board minutes. I assume there is a break even point with electric locomotives and EMUs - although I haven't read what it is. NJT runs trains with both EMUs and electric locomotives in their system, if anyone knows what the break even point is it is them.

[Patrick Boylan]

I was in Rome July-August 1976, their subway had just about every other train locomotive hauled. You guessed it, the MU's were on the shorter runs, locomotives on the trips that went longer to the suburbs, Ostia.
They may have changed things around since then, my quick google implies that the Ostia service might not share tracks with the subway service, but I'm pretty sure either MU's went in the subway all the way from the downtown main railroad station Termini to the beach, and locomotives ran from the slightly peripheral Pyramide station on the same tracks to the beach, or perhaps some locomotives also originated at Termini station.

[BuddCar711]

Amtrak is not running a Metro(suburban) service comparing them to EMU's, is like comparing Ashley Dupre' to Virgin Mary.
EMU's have on average 600 hp per car or more, and because of all wheel drive a hell of lot more acceleration than locomotive with 4 axles.

Not to mention braking because a loco is responsible for the stopping the entire train (which requires a minimum distance of 1 mile) while an M.U. consist, each car is responsible for the braking (which doesn't require distance).

[DutchRailnut]

Even on locomotives hauled trains each and every unit does its own braking, and no locomotive hauled trains do not take a mile to stop.
for example at 70 mph, a 7 car Bombardier with Genesis can stop comfortable in 1/3 of a mile, same as a M-2 or M-8.

[ExCon90]

FWIW, the City & South London Railway started in 1890 with 3rd-rail locomotive-hauled equipment and decided very quickly thereafter to change to MU. The Metropolitan Line, formerly the Metropolitan Railway, ceased using locomotives as soon as it was fully electrified. The Chicago and New York elevateds no doubt had good reason for choosing MU when they electrified rather than getting electric locomotives to replace steam.

[Station Aficionado]

FWIW, the City & South London Railway started in 1890 with 3rd-rail locomotive-hauled equipment and decided very quickly thereafter to change to MU. The Metropolitan Line, formerly the Metropolitan Railway, ceased using locomotives as soon as it was fully electrified. The Chicago and New York elevateds no doubt had good reason for choosing MU when they electrified rather than getting electric locomotives to replace steam.

Here's a YouTube video of the special steam-hauled 150th Anniversary Train on the Underground.

[BuddCar711]

Now if you're looking for a de facto locomotive hauled metro, there's the Broad Street Subway of the mid-1970s to early 1980s. the reason I've mentioned de facto is that a 5-6 car consist, 5 cars are hauled dead while the (barely) running car served as the locomotive. Those cars were literally falling apart, and somehow managed to cope with the 1980 World Champion Phillies crowd. Those were the days.

[ExCon90]

Yes, but was the acceleration as good?

[GWoodle]

This is more of a devil's advocate "why not" question, but would it make sense to run some metro lines (CTA L, LA Subway, MARTA, etc.) using [electric] locomotive-hauled trainsets instead of EMUs? Right off, I can think of two points against this: bad acceleration, and excessive current draw.

For the CTA, it is easier to operate in made up trains of 2-4-6-8 cars max. At the end of the run, the operator walks to the other end for the flip trip. Train doors are all open for passengers to board & get their seats. In winter, it is a great place to get in from the cold. As long as you have a seat, most passengers don't mind the short wait. There may be a little lag at the end of rush as longer trains get yarded in favor of shorter ones. Usually those trains are already waiting on the other platform. A locomotive to push/pull the train takes up too much non revenue space. Space in the terminal is scarce. There is no space for a wye or any other type turnaround track.

[mtuandrew]

Now if you're looking for a de facto locomotive hauled metro, there's the Broad Street Subway of the mid-1970s to early 1980s. the reason I've mentioned de facto is that a 5-6 car consist, 5 cars are hauled dead while the (barely) running car served as the locomotive. Those cars were literally falling apart, and somehow managed to cope with the 1980 World Champion Phillies crowd. Those were the days.

There's a few deliberate power car-trailer sets running around too. The South Shore comes to mind, and doesn't Metro-North have some as well? Not quite the same thing, but it has similarities.