Loco Hauled Trains, EMU's or DMU's?

[CSXfoamer1997]

Which of these is considered better for the following trains: regional, commuter, long-distance?

Longer loco-hauled trains, Electric Multiple Units (EMU's), or Diesel Multiple Units (DMU's)?

And why?

 

[CCC1007]

The answer is it depends, and that is the answer because all of the above types of services and equipment have different needs based on other factors that are so varied that it would help to narrow the search by specifying certain route(s) for analysis.

 

[cirdan]

Lots of advantages.

Lots of disadvantages.

Multiple units have better acceleration than loco hauled consists. They also have more usable space as the traction equipment is mostly below floor level.

They are also more fuel efficient as you are dragging less dead weight around.

On the other hand, especially in the case of diesel multiple units, having passengers on the same vehicle as the prime mover can lead to unwelcome vibrations and noise.

Multiple units are also less flexible as you cannot easily add or remove vehicles

So I wouldn't say one is better than the other but it depends on the use case and priorities.

 

[Seaboard92]

It all comes down to market and the best examples I can give you really are in Germany. A place that has tons of the following types. In Bayern there is the Meridian trains (the ones that crashed lately actually). They took over a commuter line from DBAG. When DB AG ran the line it was usually a double deck seven car train every hour. Now Meridian has the contract and they run three EMUs coupled together which I want to say totals out at 12 cars it might be 15. The EMU with all axles powered has great acceleration which helps shorten run time. But station work is longer due to the longer trains.

The real pros of Multiple Units

Fast acceleration

Cheeper operational costs

The cons

Not flexible to demand.

In the case of two MUs put together no way for the crew or passengers to move about the whole train.

Now we also have the high speed emus and the conventional IC locomotive hauled trains.

The ICE which is an EMU (minus the ICE 1) enjoys the high acceleration speeds and they can handle the grades really well. Then you have the IC equipment which is locomotive hauled it can grow and shrink with demand on a route. Usually that doesn't happen. And it's easier for a route with multiple splits.

CSX Foamer I recommend you visit Germany one day especially with you interested in designing equipment. It's a good place to visit. Maybe go to Innotrans in September in Berlin.

 

[Gemuser]

It really does depend on various factors including location. In some countries the distinction is very blurred. For example in Switzerland where I recently spent a month, there are almost no DMU [i've never seen any, but to be conservative I'll say almost], lots and lots of EMUs and plenty of loco hauled trains. On some railways, especially the RhB EMUs are often used as locos. On my trip on the Bernina Express from Chur to[SIZE=12pt] Tirano in Italy the "loco" was a 3 car EMU pulling 5 Panoramic cars, and this was over two major Alpine passes. EMUs pulling freight wagons was also quite common. There were other [/SIZE]idiosyncrasies[SIZE=12pt] on Swiss railways, boy were there! All very interesting.[/SIZE]

 

[cirdan]

In the case of two MUs put together no way for the crew or passengers to move about the whole train.

Disagree. You can design emus to have end gangways

 

[Seaboard92]

You are right on that one. I was thinking more about the emus I see in Europe on a more regular basis. And none of those tend to have a method at least in Germany

 

[jis]

Having the ability to walk the entire train, at least for suburban trains is vastly overrated, unless of course the trains are so lightly loaded that people can actually make major moves from one end of the train to the other. Being able to traverse the cars of each individual unit, which are often four or five cars long, is plenty of flexibility to move away from crowded cars to uncrowded ones, if there are any.

 

[Seaboard92]

I remember one suburban run I was on in Germany. From Prien am Chiemsee to München. It was a weekend train around 4pm and I was traveling on a Bayern Ticket which allows up to five for unlimited trains in Bayern all day. The train was an eight car consist of Bilevels. And it was packed. The conductors tried to get down the aisle and couldn't. People playing cards on coolers in the aisles. People sitting on the aisle. He eventually threw his arms up and I never saw him again.

 

[Touchdowntom9]

Just a general question here—if you compare 2 trains of the same total weight and same total horsepower, but the only difference is that one is an EMU or DMU that has all axles powered and the other is a loco hauled train, will they have the same exact performance or will one accelerate/decelerate faster than the other? I assume the EMU/DMU is going to accelerate faster but don’t know for certain and if it is by much

 

[MARC Rider]

Lots of advantages.

Lots of disadvantages.

Multiple units have better acceleration than loco hauled consists. They also have more usable space as the traction equipment is mostly below floor level.

They are also more fuel efficient as you are dragging less dead weight around.

On the other hand, especially in the case of diesel multiple units, having passengers on the same vehicle as the prime mover can lead to unwelcome vibrations and noise.

Multiple units are also less flexible as you cannot easily add or remove vehicles

So I wouldn't say one is better than the other but it depends on the use case and priorities.

Loco hauled trains should have more usable space, as all the traction equipment is up in the locomotive and is not present in the passenger cars.

Only permanently or semi-permanently coupled trainsets are less flexible. I would think that RDCs or Silverliners or similar equipment is just as flexible as locomotive hauled trainsets. MUs could certainly have enough power to haul a few added non-powered cars in the consist, too, if needed.

Another thing to consider is that every MU car has "traction equipment" (motors, engines, etc.) If this stuff goes on the fritz, the car must be taken out of service, whereas in a loco-hauled train, only the locos have that stuff, so if there's a problem, all they need to so is swap in a new locomotive.

 

[MARC Rider]

Disagree. You can design emus to have end gangways

Yeah, like every commuter train I've ridden on in the US.

 

[caravanman]

Loco hauled trains can't accelerate as quickly as a train with many powered axles. Part of the reason is the sudden load/strain on the couplings of the loco hauled train. Another issue is track adhesion, a powerful loco starting away quickly with a heavy load is likely to experience driving wheels slipping, rather than gripping the rail.
For commuter railroads and metros, the ability to accelerate and move a train quickly on to the next section of track can be important, as then the following trains can move forward, allowing a more frequent service.

 

[jis]

Loco hauled trains should have more usable space, as all the traction equipment is up in the locomotive and is not present in the passenger cars.

Modern EMUs as well as DMUs usually do not require any floor space (beyond what would be required in a locomotive) for the electrical gear, so this point may or may not hold depending on the vintage of the unit.

 

[Brian Battuello]

Loco hauled trains can't accelerate as quickly as a train with many powered axles. Part of the reason is the sudden load/strain on the couplings of the loco hauled train. Another issue is track adhesion, a powerful loco starting away quickly with a heavy load is likely to experience driving wheels slipping, rather than gripping the rail.
For commuter railroads and metros, the ability to accelerate and move a train quickly on to the next section of track can be important, as then the following trains can move forward, allowing a more frequent service.

There is a tiny railroad museum in Bedford MA with one piece of rolling stock, a Budd RDC. They have a very nice exhibit inside the RDC, and one of the features was that they cut about 17 minutes off the Bedford/Boston time by using the faster accelerating self contained unit instead of locomotives and coaches.

They did not say how long it takes to bicycle from Bedford to Boston after the line was discontinued and rail-trailed.

 

[jiml]

There is a tiny railroad museum in Bedford MA with one piece of rolling stock, a Budd RDC. They have a very nice exhibit inside the RDC, and one of the features was that they cut about 17 minutes off the Bedford/Boston time by using the faster accelerating self contained unit instead of locomotives and coaches.

They did not say how long it takes to bicycle from Bedford to Boston after the line was discontinued and rail-trailed.

DMU's before that was even a term. Looking back it's amazing what they were able to pack into a single railcar 70 years ago without compromising interior space or performance.

 

[Mailliw]

I think locomotive hauled trains are the best option for long-distance routes. They're more flexible and the locomotives can be swapped out as needed changing from electric to non-electric territory between railroads or between countries.

 

[Caesar La Rock]

Disagree. You can design emus to have end gangways

Multiple units can also be just as powerful as a single locomotive too, if a railway warranted that. For example, this EMU is a 4REP or Class 430/432. British Rail built these multiple units for use on the South West Main Line to Bournemouth in the 1960s. These EMUs had 3,200hp (8 English Electric 546 motors producing 400hp), which was more powerful then most locomotives British Rail had in use at that time these were in service. That 3200hp was enough to propel 4 or 8 unpowered coaches at track speeds of 90mph.

 

[cirdan]

Just a general question here—if you compare 2 trains of the same total weight and same total horsepower, but the only difference is that one is an EMU or DMU that has all axles powered and the other is a loco hauled train, will they have the same exact performance or will one accelerate/decelerate faster than the other? I assume the EMU/DMU is going to accelerate faster but don’t know for certain and if it is by much

Trains of the same weight and same power should have broadly the same acceleration. To answer this question fully one would have to look at the torque to speed curves of the motors. But seeing the DMU will probably be using electric motors too, they should be broadly identical.

The difference here though is that DMUs are typically heavier than EMUs as they have to drag around a lot of additional equipment. So for the same power they are going to have a lower acceleration and (of course depending on how the electricity is generated and transmitted) a lower fuel efficiency and higher emissions.

 

[railiner]

DMU's before that was even a term. Looking back it's amazing what they were able to pack into a single railcar 70 years ago without compromising interior space or performance.

I agree for the most part, but the Budd RDC did have those mid car exhaust 'chimney's' that also carried water to the rooftop radiators, and electrical conduits, perhaps reduced seating capacity by one row....

 

[cirdan]

Having the ability to walk the entire train, at least for suburban trains is vastly overrated, unless of course the trains are so lightly loaded that people can actually make major moves from one end of the train to the other. Being able to traverse the cars of each individual unit, which are often four or five cars long, is plenty of flexibility to move away from crowded cars to uncrowded ones, if there are any.

On longer distance trains, however, where there may be services such as a cafeteria car, being able to walk the length of the train removes the costly and inefficient need to duplicate such services. There are examples in France, Germany and Spain of trains having to have two operational cafeterias or restaurants because this was considered easier to implement than a passageway between the trains. The result is that the individual cafeteria or restaurant is smaller, has less stock, less choice, less income, but still needs to be fully staffed etc, so is going to be both less attractive and less profitable.

In the British 4-REP trains mentioned above, the R actually stood for restaurant. The passageways through the ends of the unit permitted passengers from the rest of the train to access the restaurant. Their successor trains that ply this route today do not have any food service unfortunately (but still have passageways).

The passageways also make it easier for conductors or ticket inspectors to do their job, especially on express trains that do not stop very often.

As a passenger it is also convenient to be able to walk down the train to seek another bathroom if your nearest bathroom is either occupied or out of service.

 

[AmtrakMaineiac]

There is a tiny railroad museum in Bedford MA with one piece of rolling stock, a Budd RDC. They have a very nice exhibit inside the RDC, and one of the features was that they cut about 17 minutes off the Bedford/Boston time by using the faster accelerating self contained unit instead of locomotives and coaches.

They did not say how long it takes to bicycle from Bedford to Boston after the line was discontinued and rail-trailed.

Having worked in Bedford when I was living in Massachusetts, it's a shame that line doesn't still exist, as Bedford is somewhat of a transit black hole, with only a few rush hour only buses to Alewife Red Line or the Waltham commuter rail station.

The Budd RDC has to be one of those iconic designs that has examples still running today 70 years or so since its introduction. Like the DC-3 or the PCC streetcar. So far attempts in the US to duplicate or improve on this design have not worked out (remember the ill fated SPV-2000?).

 

[jis]

As far as using DMUs on low to medium traffic routes go, it looks more and more like it will be FLIRT or equivalent going forward, as those are easy to configure with different mix of power source and at a pinch can be converted from one to another, something that was impossible to do with past standard DMUs.

Not so much in this country, but elsewhere a lot of new EMUs that are being deployed are articulated 4-8 car units with full width or close it it, gangways. I think at present we are at the cusp of very significant change in what trains will look like, and it will take a while to settle down as more experience is gained with various configurations, and incorporated in the next round of design.

 

[cirdan]

As far as using DMUs on low to medium traffic routes go, it looks more and more like it will be FLIRT or equivalent going forward, as those are easy to configure with different mix of power source and at a pinch can be converted from one to another, something that was impossible to do with past standard DMUs.

I think this perception is partially clever marketing.

In the 1970s and 1980s, British Rail Research did work on its Advanced Multiple Unit train that saw a common bodyshell platform, trucks and other components, all derived from the Mk3 coach, with all parts being optimized to work together to provide the smoothest possible ride. Most British EMU and DMU designs of that period built on this research work, but obviously the marketing guys at BREL were not as good as presenting the story this way. Also the unfortunate British tendency to want to re-invent the front end design of every class (not always to the highest standards of aesthetics) and also the interior, led the public to believe that every class had been created from scratch. Stadler are obviously smarter in this regard.

Switching out and repurposing stuff is not as big a deal as it is made out to be. Especially the Southern Region of BR (and before them the Southern Railway) were very good at repurposing anything they could get their hands on. There were thus hauled cars converted to EMUS and indeed EMUs converted to hauled cars. There were re-motorized cars, re-bodied cars, and trains that like the famous Irishman's broom, could claim to have only had their handle changed twice and the head changed three times but to still be beyond any doubt, the original broom.

In terms of manufacturers creating a platform and then individualizing solutions from that, going further back in time, one could say Budd and others also did something similar .