DMU’S seem like a no brainer for commuter rail service outside the NEC. Especially for Metra, Coaster, and Metrolink. Maybe Amtrak for Surfliner/Capital/San Juaqian services.
They were successful from the late 1950’s into the 1980’s. Budd marketed them as RDC’s and they were used in all sorts of services. Push-pulls pretty much took their place in suburban service.
Why would they be a no brainier? Each car has one or two engines and transmissions so say on a METRA 8 car train you could have 16 engines to maintain rather than one locomotive. In addition they would be considered "locomotives " for FRA inspection requirements. They might be a good choice for services requiring only a couple of cars but not for typical METRA sized trains.
Hmmmm.
Motorcoach buses use pretty much the same “hardware” (truck-sized high-speed Diesel, torque-converter transmission) as DMUs. Bus operators are happy with their buses but a DMU doesn’t work on rails because Federal inspection/multiple engines and transmissions/high maintenance costs?
Someone is going to tell me, “heh, a bus is one thing, but don’t kid yourself that engines and transmissions from a bus can stand up to the rigors or railroad operations.” That may indeed be so. So the rail being such a hard environment on equipment, tell me now, what do rail operations “bring to the table” that motorcoach buses do not?
DMUs would be especially good for service like the PRSL used to have. Start from the terminal with one train. At the first branch drop off one or two cars which will service that branch, at the second branch drop off one or two more and continue until all branches and the main are serviced.
Travel into the city is just the reverse. The train just keeps getting longer at each junction.
Lets analyze possible DMU types of operation.
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Assume that major commuter times would have dedicated trains to each destination type not important either loco or DMU.
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Those metropolitan areas that have a high ratio of final destinations to trunk lines from station(s) would be prime locations. ( south and east of boston, SE of PHL, California locations, etc )
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For off peak times a DMU train could depart and branch off car(s) to the various destinations.
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Several union and FRA changes need to happen.
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Just one possible examle:: A ten car DMU departs a central station with an engineer / conductor and 4 additional conductor / engineers. At point “A” rear crewman uses a switch to quick disconect last 2 cars. As soon a disconnect is verified trailing unit(s) crewman can do a quick brake check (maybe some kind of mechanical indicator in car ) . Front pulls away and soon as front 8 clears the diverging switch rear crewman operates switch control for his route. Repeat for all additional splits.
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Inbound dispatcher can align switch at points ( “A - M” ) to select which unit(s) are desired to lead. If a unit is waiting on diverging route he can operate switch button as soon as other units clear switch island.
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Here is where it gets complicated. Unit(s) coupling to leading unit(s) need to have a restricting speed limiter automatically activated to allow gentle couplings.
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Once the coupling is verified ( back unit may have to attempt back up to test joint )
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Front cewman can then initiate brake check having other crewmen check their units.
some other complications
OOPS web site cut some of my post will try to restore.
11. Ticket collection / v
In a word no. The PRSL lost customers from the time the Ben Franklin bridge opened and cars could drive to the shore. Now it only goes to linden and many destinations no longer have stations. If you are going to drive a third of the way why would you wait for a train to take you the rest of the way and have to hoof it when there?
So why do they make articulated busses? Why doesn’t each section have its own motor? Obviously fewer engines simplifies things. Even EMUs have given way for electric locos on NJT. And electric locos are giving way for diesels on MARC. Diesel locos are the least common denominator, and anything else needs to have its own justification.
Articulated buses having only one Diesel engine doesn’t prove anything. You could have semi-permanently coupled power/trailer car pairs. Someone commented some while ago that interurban lines found that to be a cost-effective balance.
If separate locomotives are such a great thing, why don’t subway trains use locos instead of MU cars?
MUs are useful in subways and similar enviroments because they accelerate fast and can negotiate steep grades. The main problem in today’s environment are crash regulations that require weight to be high enough that it kills most of the fuel economy advantage.
As Buslist notes, each must be inspected as a locomotive, (cab cars are similar, though). Therefore, the only place for MUs is in places where trains must be short and flexible, otherwise costs outweigh benefits.
Another reason that DMU’s lack wide industry support are the incidences of grade crossing crashes. At the same time this thread was first printed, the following topic was about MetroLink using BNSF engines instead of cab control cars. Engineers in push-pull service often privately speak of being “uncomfortable” in the cab car.
In addition to steep grades as NorthWest pointed out, there are very tight curves that subways must negotiate.
Three of the four predecessors to the Chicago Rapid Transit Company basically did just that. The fleets were a mix of motors and trailers and trains were arranged with one or two motors at the front end followed by a varying amount of trailers. The traction motors on the motor cars had a relatively high rating when compared to the cars on the South Side Rapid Transit, whose fleet was almost entirely motor cars.
DMU usage depends on line traffic density also. There are some lines in Europe where reasonably frequent short-distance transportation is desired, but the number of passengers per train does not warrant a longer, loco-hauled consist. The solution? From Stadler, the GTW 2/6, an articulated unit with a single engine (electric or diesel-electric) in a short, separate module between the front and rear passenger compartments. There is a through passage on one side of the module. The trains are modular, so longer configurations are possible. I believe these units may also be used on the DCTA in TX.
http://www.stadlerrail.com/media/uploads/factsheets/GTW_UBB_e_1098.pdf
DMUs and EMUs have different operating characteristics from loco / electric motor operation.
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MUs are good when stops are of short distance apart. They can accelerate quicker especially since HP / tractive effort is lower per powered axel lowering wheel slip. Have ridden EMU trains and they speed up much faster.
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Electric motor hauled trains accelerate somewhat slower due to only 4 powered axels but usually have a higher top speed. The track configuration of present NEC stations still allow motor max acceleration to be effective due to near station slower zones.
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The higher max speeds are important for tracks where there is mixed local and express operations. The NJT express trains that run on the NEC need the higher speed to run on Amtrak’s inner tracks otherwise they would be placed on the outer local tracks so not to delay regionals and Acelas.
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SEPTA is a good example of the type of operations of #3. Off peak trips on SEPTA are almost all MUs that make local stops some as close as 3 miles apart. That is part of its problem becoming world class operation. A few rush hour trains are haules by AEM-7s that bypass many local stops running on Amtrak’s express tracks or just in front of locals on SEPTA’s tracks.
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One concern is MARC’s desire to go with diesels on its NEC runs to Perryville and future Wilmington. MARC would retire their motors. Amtrak is not happy about that and the change in definition of the NEC might enable Amtrak to demand electric motors on the WASH - WIL route. This may be very important because MARC wants to provide more trains in future on the NEC than now.
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This will result in more trains than even PRR had during WW-2. That is on a route that has many miles of just 2 tracks some miles 3 track and very few miles 4 track. Amtrak often holds MARC trains departing o
What about the Nippon Shayiro DMU’s?They’re built to Tier 1 crash compliance as being Tier 4 EPA compliance.
What about them? Short trains were in my original response when I indicated they may be justified. Look how successful the Colorado Railcar DMU was!
i’m not going to tell you how rough the rail environment is I’m going to ask you what alternative the bus operators have to reduce the number of engines they maintain? Train operators have an alternative it’s called a locomotive!
The point being is that the bus operators don’t have the option of a locomotive (road tractor) and a train of cars (road vans), yet they somehow have lower costs than rail passenger operations?
No; his point being that a set of relatively-inexpensive HEP passenger cars propelled by a separate locomotive are cheaper than the ‘equivalent’ capacity via dedicated DMUs. That’s a different issue from whether ‘bus technology’ could be used on the rails.
I would comment, briefly, that there is a very long history of atttempts to use ‘modern’ bus construction (by which I mean something like the Yellow Coach/GMC monocoque construction with rear angle drive - not the Galloping Goose-style kludge) in rail service. It might be argued that Stout’s Railplane was an example; the NH Mack railbuses, the Evans auto-railers, no few of the lightweight trains of the Fifties, and the Leyland bus imported during the Carter administration certainly qualify. None of these can be classed as particular successes long-term. It’s fun to trot out the old NCL conspiracy theories, but at the end of the day the many arguments in favor of rubber-tired buses over interurban railways were, and are, compelling in just the ways contemporary GM ‘propaganda’ said they were. Modern buses (like the Megabus van Hools) are still more compelling … on the roads. Adapt the to run on rails – either permanently, or as hi-rail – and most of the advantages would be lost.
A permanent conversion of a bus into a “DMU” starts out with a significant handicap: the complete loss of its ‘primary suspension’ (tires on pavement). This requires either the provision of resilient wheels of some type, known to be problematic on low-tare-weight rail vehicles, or abridgement of the suspension to provide positive flange authority at all times while maintaining good ride quality and eliminati