Formations of DMUs with different max speeds

[Bastiaan]

Hello,

I wonder how train operating companies deal with the timetabling of any formation of two DMUs with different speed restrictions.

Let's take London Midland for example. A single 170 is restricted to 100 mph, but when it's running in multiple with a 153, I assume the speed is restricted to 75 mph? But when single 170s and 170+153 formations are operated on the same line, how are these different formations planned? A few options that come to mind:

1. Each service is timetabled for 75 mph, which means that a 170 always has a few minutes left. Also, using a 100 mph capable DMU on a 75 mph timetable wouldn't make much sense and it can better be used on other services.
2. Each service is timetabled for 100 mph, so a 170+153 formation is always a few minutes late.
3. Each service is specially timetabled for a specific kind of formation. So, if there's a 170+153 formation planned, it's timetable for 75 mph. If it's only a 170, the service can be a bit faster, which can be seen in the timetable. The drawback is that this means very precise planning, resulting in problems when a 170+153 turns up on a 170 only service. Also you wouldn't have a perfect hourly service pattern (but I noticed in the UK this isn't really seen as a problem ...)
4. Because of the many stops, the difference between the two speeds is hardly notable.

So this is what I was wondering. Thank in advance for you answers!

Cheers,
Bastiaan

 

[Lampshade]

It's usually timed for the slower speed, it's not unknown for EMT to run 158+156 on the Liverpool to Norwich services and they usually keep to time.

 

[The Planner]

Depends how permanent the stock diagram is on the line. If it is diagrammed more or less constantly as the 170+153, it will be timetabled for 75mph as thats the max speed.

If it runs as a 170 only, then it gains time.

If the diagram fluctuates quite often for whatever reason then it will be timed as 75mph also. An early train is better than a late one...

 

[thewolf]

Well the majority of LM's 170+153s run on Rugeley services, where the max speed is only 75 anyway (between Perry Barr and Tame Bridge-ish) - so the lower top speed won't make any difference.

Not sure about the occasional 170+153 on Worcester (,etc) runs, as that has sections of 90.

 

[rail-britain]

Usually the main service diagram is at the lower speed
Therefore any additional unit can be added

Another example are the Edinburgh / Glasgow - Inverness services
These are diagrammed for 90mph Class 158
However quite often these can be a Class 158+170 or Class 170
Even though the sole Class 170 is capable of 100mph, the benefits of that are wasted, the primary benefit is capacity

 

[Bastiaan]

Thanks for your answers. Very interesting to read

In The Netherlands we don't have such combinations now, but we've had them a few years ago as seen in this video: http://www.youtube.com/watch?v=i0XXTD06TMU. The front unit is capable to do speeds of 60 mph, while the latter unit can do around 90 mph. Theoretically the whole combination could reach 90 mph when the slower unit was led by the faster one. But officially the whole combination was restricted to 60 mph, because the gearing of the slower unit isn't capable for higher speeds. But this didn't prevent some drivers from occasionally doing 90 mph with them :P

 

[jopsuk]

rail-britain- where between Edinburgh or Glasgow and Inverness is there 100mph track?

Less of a problem where the actual route does not allow the faster unit to use its faster top speed.

 

[starrymarkb]

Apparently a 143 being led by a 158 is an interesting ride - especially when passing HSTs

 

[90019]

rail-britain- where between Edinburgh or Glasgow and Inverness is there 100mph track?

Not quite 100, but there's 95mph track on the Edinbrugh to Glasgow via Shotts route.

 

[Scotrail84]

rail-britain- where between Edinburgh or Glasgow and Inverness is there 100mph track?

Main line between Edin and Glas (via Falkirk High) is mostly 100mph line speed.

 

[David]

Parts of the Highland Main Line is 100mph as well

 

[Scotrail84]

Parts of the Highland Main Line is 100mph as well

As are certain sections of the Edinburgh - Aberdeen maine line.

 

[pemma]

It's usually timed for the slower speed, it's not unknown for EMT to run 158+156 on the Liverpool to Norwich services and they usually keep to time.

158s not attached to 153s or 156s can do Stockport-Sheffield around 3 minutes faster than the timetabled time so the timetable seems to be drawn up for 75mph running and if 158s are used they can arrive at some stations early.
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Apparently a 143 being led by a 158 is an interesting ride - especially when passing HSTs

I've been on a 144 passing a GNER service near Doncaster at speed and it certainly feels like you're on a lightweight train.

I've been on 142+150 and 142+156 combinations and if the 142 is leading the engine always seem to struggle on moving off, while if you're on the Sprinter it feels like the Pacer is trying to making it bounce against it's will.

 

[David]

158s not attached to 153s or 156s can do Stockport-Sheffield around 3 minutes faster than the timetabled time so the timetable seems to be drawn up for 75mph running and if 158s are used they can arrive at some stations early.

I don't know what the Sheffield - Stockport/Manchester services are timed for.

On the rare occasions I use the EMT service between Sheffield - Stockport/Manchester, I find that they are slower over the Hope Valley than TPE services (except those run by 170s), despite being able to go faster, thanks to SP differentials.

 

[pemma]

I don't know what the Sheffield - Stockport/Manchester services are timed for.

On the rare occasions I use the EMT service between Sheffield - Stockport/Manchester, I find that they are slower over the Hope Valley than TPE services (except those run by 170s), despite being able to go faster, thanks to SP differentials.

Some of the speed limit signs on Hope Valley definetly show 90mph for Sprinters.

 

[daikilo]

Depends how permanent the stock diagram is on the line. If it is diagrammed more or less constantly as the 170+153, it will be timetabled for 75mph as thats the max speed.

If it runs as a 170 only, then it gains time.

If the diagram fluctuates quite often for whatever reason then it will be timed as 75mph also. An early train is better than a late one...

The planner:

I assume you mean that the schedule supplied will be based on the capability of the train consist that the TOC designates. Either of these could vary per day of week as a function of consist changes and/or line availability. An alernative is to use the slowest for all days but this could lead to excessive line occupancy assumptions when higher speed stock is planned.

I also assume that if the TOC chooses to use a slower consist on an unplanned day then this could result in consequent impact to other trains and thus potential billing for the consequences of plan deviations.

 

[The Planner]

A TOC would bid for a path based on a certain type of traction, it would be highly unlikely it would bid for 3 paths of varying traction for various days of a week, it isnt worth the hassle. If there is a path for the slower traction then they get it, we can't tell them to use a different type of traction.

If they use a slower traction than bid for, then yes, they will take whatever delay minute hit there is. Virgin do this when the Pretendalino does Euston Birmingham runs.

 

[pemma]

Posted in wrong thread.