Speed differentials - HST / MU / DMU / EMU / SP / CS

[rich-leeds]

This topic has come up a fair bit in different places but as a side point. There's an old 2011 thread that's closed, so thought it worth starting a new one. Something came up that made me recheck my understanding.

From the current Sectional Appendix:

HST: Class 91 locomotives with mark 4 vehicles and DVT, classes 158, 159, 168, 170, 171, 172, 175, 180, 220, 221, 222, 253, 254 and 373
MU: Multiple Unit Trains
DMU: Diesel Multiple Units
EMU: Electric Multiple Units
SP: Classes 150, 153, 155, 156, 158, 159, 165, 166, 168, 170, 171 and 172
CS: Class 67 locomotives

At locations where more than one speed indicator is displayed, classes listed in more than one speed category shown above, may run at the higher speeds displayed.

National exceptions to MU trains

• Class 185 trains are not permitted to run at MU or DMU speeds
• Class 390 trains are not permitted to run at MU or EMU speeds
• Class 253 and 254 trains formed with less than three coaches between the power cars are not permitted to run at MU or DMU speeds

Some interesting stuff in there I hadn't realised, including that HST formations (with three or more coaches between power cars) can run at MU speeds as can Voyagers and basically anything else which is multiple unit (naturally enough, I suppose!). Class 185s must be pretty harsh on the lines to be the only DMU or DEMU not to be able to take advantage of MU speeds. Must be a factor on where they might end up when TPE start releasing them.

The 158/159 and 17x classes are also surprisingly flexible, being able to take advantage of any speed differential except EMU (obv!) and CS.

Anyone know the background to CS? That's a new one on me.

I'm assuming the new Hitachi 80x classes take advantage of MU, but not HST. I double-checked the Western SA, and it remains silent on them, so seems reasonable.

 

[Bald Rick]

Someone else will no doubt correct me, but the reasoning behind the categories is slightly different:

HST relates to braking performance (Appendix 3 of the relevant signalling standard)

MU, DMU and EMU relate to route availability (principally axle loading), and braking performance (Appendix 2 of the relevant signalling standard)

SP relates to route availability (principally axle loading), and braking performance (Appendix 3 of the relevant signalling standard)

No idea about CS, although I remember some fruity discussions about permitted speed with EWS when they bought them.

 

[Bevan Price]

Don't know if they still exist, but there used to be locations where Voyagers / Meridians were not allowed to run as fast as Sprinters or other MUs. I think these included part of the Preston - Blackpool North & Hope Valley lines.

 

[Class 170101]

Don't know if they still exist, but there used to be locations where Voyagers / Meridians were not allowed to run as fast as Sprinters or other MUs. I think these included part of the Preston - Blackpool North & Hope Valley lines.

Peterborough to Norwich, Class 222s run at loco Hauled speeds so slower than SP speeds..

 

[Kneedown]

Peterborough to Norwich, Class 222s run at loco Hauled speeds so slower than SP speeds..

Same over the Hope Valley, although no time is lost on that route.

 

[_toommm_]

The 185s are incredibly heavy, hence why they can't run at the higher MU speeds in the Hope Valley, and the difference is quite noticeable.

 

[matacaster]

The 185s are incredibly heavy, hence why they can't run at the higher MU speeds in the Hope Valley, and the difference is quite noticeable.

Agreed, but surely they also have more than enough power to offset their weight.

 

[Tomnick]

They can’t benefit from the SP differentials so they’re noticeably slower over some parts of the line, but they can get up to linespeed much more quickly on the substantial gradients, which must offset that - 15x units struggle to get to the lower speed over some sections, let alone the higher SP speeds.

 

[hexagon789]

I could be wrong but doesn't CS stand for Caledonian Sleeper?

When the 67s first started working the Caledonian Sleeper to Fort William they had to be restricted to lower speeds than the 37s in some places (certain bridges and things) because if their higher axle loading. Their greater power meant they could still keep time though.

Otherwise I can't see what the CS restriction would be for.

 

[DarloRich]

CS: Class 67 locomotives

Caledonian Sleeper locos in the highlands?

 

[hexagon789]

Caledonian Sleeper locos in the highlands?

I'm sorry? I don't quite see what you mean?

 

[DarloRich]

I'm sorry? I don't quite see what you mean?

The quote relates to the OP asking about CS speeds. I am mirroring your post ( which didn't read before posting mine)

 

[hexagon789]

The quote relates to the OP asking about CS speeds. I am mirroring your post ( which didn't read before posting mine)

And I should learn to read other people's posts better. I thought you had quoted me!

Never mind.

 

[scotraildriver]

There are a number of structures on the West Highland line where Class 67s were limited to 10mph when they worked the Caledonian Sleeper hence a special CS restriction.

 

[hexagon789]

There are a number of structures on the West Highland line where Class 67s were limited to 10mph when they worked the Caledonian Sleeper hence a special CS restriction.

Exactly what I was thinking of.

 

[_toommm_]

Agreed, but surely they also have more than enough power to offset their weight.

It's also about the impact on the track that a heavy fast moving object would do, plus heavy vehicle equals extended braking time.

 

[craigybagel]

There are of course also local exceptions. AIUI 67s + MKIIIs have dispensation to run at MU speeds for at least some of the differentials on the Marches line.

 

[hexagon789]

There are of course also local exceptions. AIUI 67s + MKIIIs have dispensation to run at MU speeds for at least some of the differentials on the Marches line.

Similar on the Chiltern mainline, I believe loco-hauled trains are otherwise limited to 75 mph on much of the route.

 

[Senex]

They can’t benefit from the SP differentials so they’re noticeably slower over some parts of the line, but they can get up to linespeed much more quickly on the substantial gradients, which must offset that - 15x units struggle to get to the lower speed over some sections, let alone the higher SP speeds.

Does anyone know the full story of how TPE came to get DMUs with a genuine 100mph to speed that were unable to user permitted higher speeds on long sections of the routes they were obtained for? It seems they can work to their full potential only on the WCML, the ECML, and the core trans-Pennine section from Manchester to Leeds.

 

[craigybagel]

Does anyone know the full story of how TPE came to get DMUs with a genuine 100mph to speed that were unable to user permitted higher speeds on long sections of the routes they were obtained for? It seems they can work to their full potential only on the WCML, the ECML, and the core trans-Pennine section from Manchester to Leeds.

Even on that section they don't do 100. Top speed IIRC is 85, and even then only a short dash through Standedge tunnel.

They could keep to the same timings as the 158s they replaced owing to their much greater acceleration, so their limited potential to run at full speed wasn't seen as much of an issue.

 

[rich-leeds]

Someone else will no doubt correct me, but the reasoning behind the categories is slightly different:

HST relates to braking performance (Appendix 3 of the relevant signalling standard)

MU, DMU and EMU relate to route availability (principally axle loading), and braking performance (Appendix 2 of the relevant signalling standard)

SP relates to route availability (principally axle loading), and braking performance (Appendix 3 of the relevant signalling standard)

No idea about CS, although I remember some fruity discussions about permitted speed with EWS when they bought them.

This is a really helpful in terms of understanding the various issues - cheers. Others have now clarified CS as being a restrictive differential applying to Caledonian Sleepers hauled by Class 67s on the West Highland Line.

 

[hexagon789]

There's also WES - applies to Class 442 originally, I think 444s and 450s are allowed to use these? I think it effectively permits 100 mph on parts of the line out to Bournemouth via Woking that are otherwise 90.

Then there are ones which like CS, restrict speeds to a lower value rather that permitting higher speeds:

LH - Loco-hauled
S7 - London Underground S7-stock
LUL - EMUs fitted with tripcocks and London Underground trains