What's the attraction to TOCs of EMUs?

[JonD]

Hi All,
I was looking at the IEP discussions and I wondered why there was a shift towards EMUs these days over loco-hauled services. I don't have any axe to grind, but on an engineering level

a) it seems to complicate a larger number of vehicles (carriages with traction equipment instead of just locos),

b)it would seem to limit your options for train formations

On the passenger side having all that traction equipment on a carriage adds noise and costs space.

Is it all down to getting more powered axles? I can't for the life of me see any other reason it would be attractive...

Best regards
Jonathan

 

[EM2]

Logistics, for a start. Unless you top'n'tail loco-hauled workings, you need either a second engine to take the train back the other way or space (and time) to run round.

 

[jopsuk]

For high-speed, it's for more powered axles- look at the Shinkansen units, the forthcoming French AGV, the Siemens Ice 3/Velaro etc. The older TGV and ICE sets are of fixed-formation

Add in the logistics (no runaround needed). Also, more passenger capacity for the same train length- a ten car electric IEP will be near-enough the same length as a class 91, nine Mk4 passenger cars and a Mk4 DVT, but with the addition of passenger accomodation in the front and rear cars.

It's hardly a new thing, though is it? Commuter stock has MU, especially in electric areas, for a very long time. On Intercity operations, the HSTs were originally classed as MUs, and operate in semi-fixed formations; similarly, the Mk4 stock on the East Coast and Mk3 on the Great Eastern are arranged as fixed-length, fixed formation rakes.

 

[Phoenix]

Well as we all know my opinion is pure speculation but I belive it is because.

1.Faster acceleration.
2.Lower maintainence costs.
3.More workers in general who have knowledge of the traction.
4.Higher reliability.

So this is Emu's compared to Loco hauled mind you I prefer the locos on the duties they deserve and vice versa for the Emu's.

 

[Daimler]

I was under the impression that one main reason was that Network Rail charges less for EMUs than it does for locos + stock. However, I hear this is going to change!

 

[generalvegitable]

i think it would be something to do with capacity, of course a 4 car mu would take up less space in a platform than a loco with 4 cars, mus also accelerate quicker, and have more traction with more diving wheels

 

[Pumbaa]

a) it seems to complicate a larger number of vehicles (carriages with traction equipment instead of just locos),

b)it would seem to limit your options for train formations

c) On the passenger side having all that traction equipment on a carriage adds noise and costs space.

a) complicated maybe, but less chance of a failure theoretically. However, as the units have become more complicated and technology dependant, failure rates are still quite high!

b) Possibly, but it does make lengthening formations a more simple task, not to mention fixed formation classes give the planners less headaches. Also on an infrastructure POV, it would be nigh impossible to lengthen a train by 2 coaches at a termini, with all the fiddle of removing the loco, shunting coaches etc

c) Most really don't care I think, as long as something turns up to take them to work!

 

[jopsuk]

Alos, when lengthening a MU train (by adding another unit) you don't drastically change the performance of the train (or shouldn't), as you increase the power (limited by the overhead/3rd supply, of course) and brake force proportionally, whereas adding more carriages to the back of a loco-hauled train impacts the power/weight ratio.

In reponse to Pumbaa's "b)" there though, I believe that trains were frequntly lengthened at teminii, before the loco was attached (having run around using the release siding- now removed, often to allow more or wider platforms). There were usually carriage sidings near major stations with spare stock for the purpose, and shunter locos for the purpose. Fiddly, but done a lot.

 

[Pumbaa]

In reponse to Pumbaa's "b)" there though, I believe that trains were frequntly lengthened at teminii, before the loco was attached (having run around using the release siding- now removed, often to allow more or wider platforms). There were usually carriage sidings near major stations with spare stock for the purpose, and shunter locos for the purpose. Fiddly, but done a lot.

Yes - my response was from a modern perspective, with the answer based on the differences between then and now. As much as I'd like to see it happen, I don't think it ever could!

 

[whoshotjimmi]

There is a lot of talk of commuter EMU's which have been around for many years and (mainly) have not replaced loco hauled stock. The exception that springs to mind is the Gatwick Express.

It reads to me as if the op is talking about things like the Pendolino replacing class 90 + Mk3 stock on WCML. Running EMU's on these kind of services does not, on the face of things, offer significant advantages over hauled stock. The tilting system would probably work much better on fixed formation traffic - the APT was an EMU - but using locos and DVT's works just as well. An EMU, therefore, MUST provide significant advantages over more traditional methods; cost has to be a factor as well as ratonalisation - how many sub classes of locos are there?

Were it not for the introduction of DVT's, we would still be in a world of inefficiency. There is also the ability to have a 9 car EMU all containing passengers fit into the same space as 2+7 hauled stock. More passengers per train - greater profit margin.

 

[O L Leigh]

It's not just about profit margins. Doing away with those pesky locos and DVT's eating up platform space is a quick and easy way of increasing capacity without the need to change the infrastructure.

O L Leigh

 

[The_Rail_WAy]

I suppose there are a number of advantages of running an EMU over a loco-hauled service, some of which I have outlined below:

(1) Cheap to run and maintain locos and track.
(2) Highly reliable.
(3) Fast acceleration and high speeds can be maintained.
(4) Quiet - enabling late night runnings in residential areas.
(5) From an environmental perspective they are pollution free.
(6) Better overall passenger comfort - smoot ride, not as noisy, modern designs, etc.

 

[metrocammel]

I suppose there are a number of advantages of running an EMU over a loco-hauled service, some of which I have outlined below:

(1) Cheap to run and maintain locos and track.
(2) Highly reliable.
(3) Fast acceleration and high speeds can be maintained.
(4) Quiet - enabling late night runnings in residential areas.
(5) From an environmental perspective they are pollution free.
(6) Better overall passenger comfort - smoot ride, not as noisy, modern designs, etc.

They are all very sweeping, subjective comments though! Fair enough, No.1 is probably right, but where are the figures to back the statement up? No.2 depends entirely on the EMU, as with 3 & 4. No.5 isn't really true, as the power has to be produced somewhere (unless you don't count Fossil Fueled PSs as 'pollution producing' ) - albeit not within the unit itself (as per DMUs)- also, using that logic, why is an EMU an advantage over an electric? No. 6 is also very much down to the EMU. Who's to say a SR electric unit provides better comfort, and smoother rides than you'd expect in, say, a hauled mk3 coach?!

 

[mbonwick]

I think what he means by pollution free is that EMUs don't tend to clag out stations!

 

[MCR247]

(5) From an environmental perspective they are pollution free.

Sorry, but how would a say Class 90 make more pollution than a 390?

 

[The_Rail_WAy]

Sorry, but how would a say Class 90 make more pollution than a 390?

I was listing the advantages of EMU services in general and in point 5 was highlighting the notion that EMU services cause less direct pollution than diesel powered services, as mbonwick stated they don't clag out stations etc.

Although I am fully aware fossil fuels are used to power the electricity in overhead wires/3rd rails etc I always thought the EMU's were viewed as being environmentally friendly and pollutant free. Quite important in a day in age when being 'environmentally friendly' is the green way to be.

The_Rail_WAy

My 300th post!!!

 

[JonD]

Interesting points about the problems of wasted space at terminii due to loco and DVT, and the joining/seperating of units partway through a journey. But I don't understand:

a) how is a carriage with embedded traction simpler to maintain than a seperate loco??
b) how is a carriage with embedded traction quieter and more comforable than a standard loco-hauled carriage? The noise from the traction gear, and the fact the air conditioning often gets relegated to the roof space instead of under the floor (due to said traction gear) surely must increase noise?

Obviously the latter is understandably not a major concern for TOCs.

Regarding pollution I'm not thinking about diesel locos, but electric.

The issue of high speed operation is also a bit misleading. The examples given, the APT and especially because although the APT had mutliple power cars inside the formation as opposed to locos, they were non-passenger vehicles, and so pretty much effectively loco-hauled. Indeed their successor the IC225 is exactly that.

Best regards
Jonathan

 

[gordonthemoron]

In reponse to Pumbaa's "b)" there though, I believe that trains were frequntly lengthened at teminii, before the loco was attached (having run around using the release siding- now removed, often to allow more or wider platforms). There were usually carriage sidings near major stations with spare stock for the purpose, and shunter locos for the purpose. Fiddly, but done a lot.

As I work/live near Munich Hbf I see this practice daily. Whilst a lot of continental trains have DVTs, an engine at each end or are of a fixed formation (ICE/TGV), there are still quite a lot of trains here which have a single loco at one end without a DVT (e.g. ALEX, FS, SBB, OBB & some DB) plus most night trains have only one or more engines at one end. As Munich HBF is a terminus, a new loco will be attached to the backend and the engine located at the concourse end is detached before the train departs. Coaches can also be added but only at the back end. In order to achieve this, Munich Hbf has many sidings just outside the station containing spare locos and coaching stock. It also helps that it has about 30 platforms.

 

[GB]

b) how is a carriage with embedded traction quieter and more comforable than a standard loco-hauled carriage? The noise from the traction gear, and the fact the air conditioning often gets relegated to the roof space instead of under the floor (due to said traction gear) surely must increase noise?

I was on a 360 the other day, by far the loudest noise was the constant output of the air conditioning unit. Once this was shut off (albeit for a few seconds) the train was almost like it was gliding, it was smooth and I couldn't hear a thing.

 

[The Box Photter]

Interesting points about the problems of wasted space at terminii due to loco and DVT, and the joining/seperating of units partway through a journey. But I don't understand:

a) how is a carriage with embedded traction simpler to maintain than a seperate loco??
b) how is a carriage with embedded traction quieter and more comforable than a standard loco-hauled carriage? The noise from the traction gear, and the fact the air conditioning often gets relegated to the roof space instead of under the floor (due to said traction gear) surely must increase noise?

Obviously the latter is understandably not a major concern for TOCs.

Regarding pollution I'm not thinking about diesel locos, but electric.

The issue of high speed operation is also a bit misleading. The examples given, the APT and especially because although the APT had mutliple power cars inside the formation as opposed to locos, they were non-passenger vehicles, and so pretty much effectively loco-hauled. Indeed their successor the IC225 is exactly that.

Best regards
Jonathan

Has anyone considered that in the current franchise/Rosco/TOC environment, there is no real incentive for trains to be as simple and reliable as possible. A simple loco+10 carriages would not be "valuable" enough to command high leasing costs. Whereas an all-singing, all-dancing (all-failing) Pendolino can command a much higher lease cost because of the "technology bling-factor".

IMHO, no-one has yet surpassed the comfort factor of a well-maintained Mk3 running over properly maintained and canted track.

The environmental benefits of electric unit traction are largely illusory, unless the electricity is generated using nuclear power which has no carbon emissions.

The APT-P was forced to have two identical sub-trains separated by two power cars so that 10,000 or-so horsepower was available to get up Shap & Beattock at 125 mph. Safety regulations at that time prohibited the use of a "power bus" to distribute power to individual traction motors as the current IEP (or whatever its being called this week) proposes.

Just build more HSTs and Mk3s or another batch of Class 87s and Mk3s. The idea that everyone wants to travel at 140mph is rubbish since most of the time the track is not capable of supporting that speed. I'd be quite happy to travel at a max of 110 mph so long as I knew my train would arrive on time and I'd have a better chance of being seated for the whole journey. Why is there a constant need to reinvent the wheel every time there are proposals to build new stock for any particular route. How much time has running Pendolinos on the WCML shaved off the London-Glasgow schedule? Assuming that the track has now been upgraded to the best condition it can be, I'd like to see what an HST could achieve over the same route.

I really don't understand the economics of leasing horrendously expensive and so far pretty unreliable fixed-formation trains in preference to having run-round facilities at major termini or using push-pull. Experience has shown that push-pull is perfectly safe up to 125 mph on the ECML and it has run successfully at 140+ mph too.

Perhaps some contentious points, but I stand prepared for a flaming!

 

[Moodster020]

Has anyone considered that in the current franchise/Rosco/TOC environment, there is no real incentive for trains to be as simple and reliable as possible. A simple loco+10 carriages would not be "valuable" enough to command high leasing costs. Whereas an all-singing, all-dancing (all-failing) Pendolino can command a much higher lease cost because of the "technology bling-factor".

IMHO, no-one has yet surpassed the comfort factor of a well-maintained Mk3 running over properly maintained and canted track.

The environmental benefits of electric unit traction are largely illusory, unless the electricity is generated using nuclear power which has no carbon emissions.

The APT-P was forced to have two identical sub-trains separated by two power cars so that 10,000 or-so horsepower was available to get up Shap & Beattock at 125 mph. Safety regulations at that time prohibited the use of a "power bus" to distribute power to individual traction motors as the current IEP (or whatever its being called this week) proposes.

Just build more HSTs and Mk3s or another batch of Class 87s and Mk3s. The idea that everyone wants to travel at 140mph is rubbish since most of the time the track is not capable of supporting that speed. I'd be quite happy to travel at a max of 110 mph so long as I knew my train would arrive on time and I'd have a better chance of being seated for the whole journey. Why is there a constant need to reinvent the wheel every time there are proposals to build new stock for any particular route. How much time has running Pendolinos on the WCML shaved off the London-Glasgow schedule? Assuming that the track has now been upgraded to the best condition it can be, I'd like to see what an HST could achieve over the same route.

I really don't understand the economics of leasing horrendously expensive and so far pretty unreliable fixed-formation trains in preference to having run-round facilities at major termini or using push-pull. Experience has shown that push-pull is perfectly safe up to 125 mph on the ECML and it has run successfully at 140+ mph too.

Perhaps some contentious points, but I stand prepared for a flaming!

The TOC's have a Bus-train fetish, & can't help themselves!

I Concur with you points, btw. The bit in bold particularity so.