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.
zkr123 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.
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?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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.
1. Assume that major commuter times would have dedicated trains to each destination type not important either loco or DMU.
2. 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 )
3. For off peak times a DMU train could depart and branch off car(s) to the various destinations.
4. Several union and FRA changes need to happen.
5. 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.
6. 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.
7. 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.
8. Once the coupling is verified ( back unit may have to attempt back up to test joint )
9. 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 / verification would wait for second crewman or maybe use british method of turnstiles.
12. Coupling shoud be at stations with diverging switchs located just outbound of platform end.
13, For inbound dispatcher can set diverging switch to allow whatever unit is desired to lead with override if he gets it wrong.
14. If planned trailing unit(s) are waiting at switch trailing crewman can operate switch to allow coupling.
15. Leading unit should have platform car markers so does not require trailing unit more distance to travel than necessary. ie 2 cars 3 cars etc .
16. Trailing unit needs some kind of automatic coupling speed limiter for coupling.
17. Destination signs on all units a must.
Paul Milenkovic 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?
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.
Paul Milenkovic If separate locomotives are such a great thing, why don't subway trains use locos instead of MU 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
C&NW, CA&E, MILW, CGW and IC fan
DMUs and EMUs have different operating characteristics from loco / electric motor operation.
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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 out of WASH anytime MARC will be ahead of an Acela 8 minutes or less. That is so MARC will not delay the Acela or express regionals which have been told is 6 minutes or less.
7. What is MARC's solution ?
a. Get new motors probably new ACS-64s.
b. Take the delays and not get more rush hour slots.
c. Pay most of cost to make WASH - Wilimington 4 track that includes the 3 two track draw bridges in Maryland. To not interfer with Amtrak Marc still would see many express trains on outside tracks. If MBTA plans more trains to Providence they may come up against the same problems.
d. MARC might need trains to be equipped with 2 locos.
e. But MUs on MARC no chance. MUs on NJT certain lower population areas might enable MU split operations non rush hour but still change a Newark Penn.
What about the Nippon Shayiro DMU's?They're built to Tier 1 crash compliance as being Tier 4 EPA compliance.
zkr123 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?
Paul MilenkovicThe 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 elimination of NVH. Then we get into different lateral-accommodation characteristics, and the associated nasty tip-over problems with the very reduced vehicle track if a double-deck bus is to be operated on standard gauge.
All this before we get into labor issues, cost of terminal facilities and access, reasonable convenience of stops to actual passenger circulation patterns and travel preferences... the stuff that actually makes money out of the technology. I have a real clear picture that you will be able to hire non-union 'drivers' who have to learn a piece of railroad, follow rules, etc., and maintain required paperwork -- care to bet on whether you'll get a waiver from the FRA 'locomotive' recordkeeping with bus lines lobbying Congress and the administration? -- and then provide the necessary timely service at cheap price to get the railborne bus service competitive 24/7 with the rubber-tired equivalent running on the public road infrastructure (or dedicated busways).
Meanwhile, anywhere you can begin to make a case for "bus DMU" service, you're likely either to have a strong case for at least some conventional commuter-train density during rush hours, or electrification (with subsidy) to reduce pollution. The former would require your bus to be FRA buff and draft qualified, and even with really, really good crash energy management as an 'alternative', designing a bus that can survive the expected head-on with a conventional train is decidedly non-trivial, with very little practical or economic utility either for the design expenses or 'work product', outside the specific niche of railbuses.
Now, I for one am more of a fool. I do think there are very particular markets for both single and artic 'bus conversions' or bus-grade lightweight railcars in this country, particularly where off-peak service at reasonable frequency is to be provided in known passenger corridors. I would also expect many of the same markets for fast service in congested regions, or areas not well served with arterial roads, that were proposed for the Leyland bus in the late '70s. The thing is, if there is any particular success, expect the same thing to happen as during the streamlined motor-train era: anything that 'pays' will pay well enough to get real trains, with their associated economies of scale. And when that happens, expect the use of railbus technology to become incompatible with the higher-capacity trains even if they are built to "DMU" standards and not full FRA-legal strength.
Something worth considering,perhaps: what amenities should (or could) be put into bus-construction 'trains' that would make them preferable to pure-bus competition? I took a perhaps-misguided interest in the era of 'premium' bus services like those of the Pickwick Nite Coaches, where you at least nominally had a steward, en-route food and beverage service, and sleeper accommodations in a comparatively small vehicle. That suggests that premium-level accommodations between some city or destination pairs might be possible ... at the right level of comfort or amenities. If a railbus has the ability to operate more artic segments from the same 'power capsule' or adapted axle drive than a conventional bus of comparable construction would - which seems likely to me -use of some of the added space for things like real business class or good-quality food and beverage service ought to be practicable.
Problem is, I don't think companies like Stagecoach could be induced into purchasing these vehicles, even with government assistance, unless some guaranteed level of profit or else subsidy were assured. On the other hand, there are some very clear opportunities for the Megabus operating model ad-hoc routes as traffic warrants, point-to-point service from cheap rather than particularly convenient street locations, with very limited stops) using functionally-underutilized rail corridors. Provided the traffic for the larger vehicle produces greater profits than the same capacity in 'normal' buses with logical enhancements in self-driving capability.
The argument has been made that the Budd RDC was "unsuccessful", but how unsuccessful was it?
Its main market was to replace the 10-Wheeler-with-a-combine-and-a-coach consist in local and branchline service, and it did this quite well. Only the RDC was introduced at a time when those branchlines were drying up, if there ever was a time when they were a cost-effective proposition.
These branchline trains, whether propelled by 4-6-0 locomotive or by underfloor 2-stroke Detroit Diesel, were in turn superceded by bus lines, which in turn were superceded by "friend or relative giving you an automobile ride from Algoma to Austin-Straubel in Green Bay."
The "standard" Amtrak corridor consist for the longest time had been a push-pull of a Genesis locomotive followed by 4 Horizon or Amfleet cars with a depowered F40 "cabbage car", ballasted with cement to sit right on its springs with the prime mover removed, bringing up the rear.
So you have 250 tons of locomotive/cab car attached to 240 tons of corridor passenger stock? With no attention paid to streamlining, especially the height steps between locomotive and train car and the underbody of the train car, and tell me if you see this same thing on an intercity motorcoach on something run at lower speed (70 MPH vs 80 and soon-to-be 110 or even 125 MPH for the train). And this is more cost-effective than a consist of DMU's using off-the-shelf truck engines and transmissions?
I got scolded by someone in the local passenger-train advocacy group that I wanted to kill train crews (and passengers) by replacing these overweight over-powered consists with DMUs where driver and front-car passengers are exposed in a grade crossing collision.
There was a time in the 1990s when Alan Cripe was promoting a Diesel (i.e. DMU) version of the United Aircraft TurboTrain, which in turn was a gas-turbine version of a Diesel-motor-train proposal by Cripe for the C&O in the 1950s. TurboTrain or its never-built truck-engine-and-transmission version didn't have all axles powered, and the consist was single-axle articulated, but short articulated consists could be conventionall coupled at the retractable clamshell nose doors at the ends. You have the same thing in Wide Cab (or safety cab) road switchers, where a nose door allows crew access from the cab to the front platform in the absence of the road switcher style outside gangways.
Another member of that same group must have been at a sales promotion of this concept, telling of "the video they showed of that nose slicing through a truck at a grade crossing." Jason Shron writes in his book about this grade crossing collision of the Canadian TurboTrain on its maiden trip full of press people, providing an unexpected proof-of-concept of the ruggedness and safety of this ultra-lightweight train.
So the grade-crossing collision problem can be solved with a TurboTrain-style "wide cab", one where short consists can be coupled into longer ones with the signature Alan Cripe design of a passenger passageway in between.
Oh, there is the FRA locomoive/power car inspection. I mean, how onerous could that be compared to say, the highway patrol safety inspection of an intercity motorcoach?
It is all the same-old-same-old that the passenger train in its locomotive with HEP from Ben Heineman's Chicago and North Western in the late 1950s is practically perfect in every way, there are no improvements to be had, and by the way, passenger trains cannot operated without substantial subsidy and if you think differently, you are painfully ignorant.
Budd didn't aim the RDC strictly at the branchline and local services, it just turned out that way. Consider the "Daylight Speedliner" on B&O and the proposal for bus-frequency service with RDC's on the ATSF Transcon. The "Daylight Speedliner" got caught up in the general decline of passenger service and the ATSF proposal died after the RDC derailment on the Surf Line, which caused ATSF to sour on RDC's.
I've spent a lot of time in Ireland and the UK over the past two years. Both countries, especially Ireland, use a large number of DMU. I understand the maintenance issues of 1 locomotive versus engines under every coach. There must be a reason that DMUs are welcome in these countries but not in the US.
I was going to mention how both railways handle food differently then Amtrak but the topic of eating and riding trains seems to be very emotional!
ndbprrI don't think the public will buy a "rail"bus. The aerotrain bombed primarily due to its hard riding characteristics.
What makes you think that the hard riding was intrinsic to adapting a bus body and had nothing to do with a naive design for a 4-wheel passenger car that did not take into account rail-wheel dynamics?
Paul Milenkovic ndbprr I don't think the public will buy a "rail"bus. The aerotrain bombed primarily due to its hard riding characteristics. What makes you think that the hard riding was intrinsic to adapting a bus body and had nothing to do with a naive design for a 4-wheel passenger car that did not take into account rail-wheel dynamics?
ndbprr I don't think the public will buy a "rail"bus. The aerotrain bombed primarily due to its hard riding characteristics.
Historically extremely lightweight cars have had poor ride qualities. It seems that the minimum spring rate for trucks to operate successfuly is too high to give good ride qualities to very lightweight car bodies.
Never too old to have a happy childhood!
Historically, rail-wheel dynamics and getting good ride quality at speed was purely cut-and-try with theoretical treatments by Carter and others not widely known.
These days with the emphasis on HSR by our major trading partners, people engaged in designing new passenger trains better know what they are doing. Much or most of the passenger trains outside US borders are "lightweight" by US standards and ride smoothly, although maintaining the track and especially the surface profile of the rail head has something to do with it.
The Aerotrain was a particularly naive design (as in not understanding underlying physical principles) that rode especially badly. So a GM bus (back in the day) rode on 2 axles and was reasonably smooth. Let's take a bus body and put two rail-wheel axles on it along with those bus air springs. Same thing?
Not the same thing. The vehicle dynamics that steers a bus are entirely different from those of a rail vehicle. Leaving aside the steering corrections from the human driver, the rail vehicle has solid axles connecting pairs of wheels (in everything apart from Talgo) that exhibit "kinematic hunting."
The Talgo train sets are light weight and ride on a single axle between cars and ride well. So it can be done. Takes significant maintenance.
Also, when in Great Britain, rode in DMU's that met and combined into longer trains of DMU's enroute to London. On the former BCRail from Vancouver to Prince George, they routinely ran a four car train of RDC's out of North Vancouver to Lilloett, dropped two cars which returned to N. Vancouver while the front two continued North to Prince George. Great operation. Cost effective. But time cought up with them. The RDC's wore out and it was before the Colorado Railcars.
Paul MilenkovicNot the same thing. The vehicle dynamics that steers a bus are entirely different from those of a rail vehicle. Leaving aside the steering corrections from the human driver, the rail vehicle has solid axles connecting pairs of wheels (in everything apart from Talgo) that exhibit "kinematic hunting."
But my understanding was that the 'observed' problems with the Aerotrain's ride had little if anything to do with kinematic hunting, except insofar as it 'coupled' mechanically into oscillation of the carbody in the vertical or horizontal plane. The issue with the Aerotrain (again, as I thought) was lack of effective damping on motion in those planes, particularly the vertical plane, perhaps leading (with high 'exciting' energy from lack of bus 'primary suspension' in the tires) to bouncing the air springs. This is where the lightweight 'bus body' construction becomes a critical element in ride quality that no amount of careful suspension design that does not involve damping or perhaps resonance breaking can help. Something I have not seen discussed in books on the Aerotrain was the exact nature of the 'substantial 'improvemenst' GM made on a car inserted into the Aerotrain after it started operating in the West (did I not read this in the Kratville book on Union Pacific streamliners?). This was touted by GM as providing much-improved ride quality. What did the improvement consist of, and what was the stated (or implicit) logic behind it? Are there clear pictures that show the improved design and its features?
More interesting to me are some of the dynamical reasons why the "Michelines" failed over here although at least a qualified success in France. The design implicitly depended on deflection of the 'tread' to produce the self-steering without continuous tread contact (my father told me about railfans in the '70s who rediscovered this effect with their Chevy Nova, which had almost exactly the same 'track' as standard gauge, and could be driven for miles on rails without touching the steering wheel (I shuddered greatly at this, but it was a different era!) Apparently there were problems with 'flat tires' (even though the special Michelin tires had very restricted air chamber height and greatly reinforced tread, and were specifically designed for the reversing distortion involved in the curving under load that generated the self-steering) and also with wheels bouncing off the track -- both of which argue for resonances in "tire bounce" analogous to what might be observed in the Aerotrain's bus-derived approach. (Of course, there isn't a good way to stop tire bounce with '30s technology, which would account for the quick disappearance of any Micheline solution as observed in the United States.)
My own feeling is that if GM had gotten into magnetorheological development a couple of decades earlier they would have had an ideal and almost tailor-made solution to vertical and lateral damping for these trains without causing NVH due to overdamping at times stiff compliance is not needed. Interestingly the development of practical MR (at an agency of the Federal government) was roughly contemporaneous with the PRR T1, almost a decade before the Aerotrains, and I don't think there are any problems with modulating the system that equally contemporaneous accelerometric techniques could not have dealt with.
If I remember correctly there were major issues with lateral damping on the Amfleet type I ride at high speed - probably involving the relative lack of damping on the secondary suspension air donuts for motion in the horizontal plane. How was that fixed?
I'm late to this thread and have only skimmed the replies, but I see no mention of the DMUs already enjoying success on commuter systems in Austin, TX, Ottawa, ON, in Southern California (connecting with Coaster service north of San Diego) and a few others I can't recall. Can anyone who's ridden any of these systems give a first-hand account?
As mentioned already, DMUs work best on more lightly traveled lines (branches), not heavily traveled systems like Coaster, METRA, Metrolink, etc.
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