Is there a case for re-aligning the track through Burton on Trent?

[trentvalley]

The north bay served the now-lifted line to Tutbury. I believe the south bay was for trains to Walsall via Lichfield. The Lichfield line still connects to the main line at Wychnor, and is used as an occasional diversionary route for XC services towards B'ham. Extending the Cross City line is new to me - it would presumably mean electrification, but would still be much slower than the direct route via Tamworth, unless they're counting on people wanting to travel between Burton and Lichfield/Sutton Coldfield.

http://wmre.org.uk/media/14045/west-midlands-rail-report-final-version-jan-2019.pdf

Listed here as after HS2 PHASE 2b as that's when there would be the capacity on the Birmingham - Derby line.

 

[DynamicSpirit]

The fuel cost can be quite significant. For a restriction like this, at an educated guess, it would be in the region of £20 per non stop train. That’s about £1000/ day, £300k pa.

If I've understood this correctly, you're saying that for a Voyager to accelerate once from 50mph to 125mph costs £20 of fuel more than it would cost for that same Voyager to travel that same distance at a constant 125mph. That can't be correct, surely? For a typical car, £20 would buy enough fuel to travel something like 100 miles (complete journey, including all accelerations during the journey and all cruising at constant speed).

 

[DynamicSpirit]

Extending the Cross City line is new to me - it would presumably mean electrification, but would still be much slower than the direct route via Tamworth, unless they're counting on people wanting to travel between Burton and Lichfield/Sutton Coldfield.

I would assume they are expecting combination of various flows: As you say, Burton-Lichfield/Sutton Coldfield. New passengers from serving Alrewas. Derby-Lichfield/Sutton Coldfield and Burton-Rugeley/Stafford potentially becoming quicker than currently possible (obviously, depending on connections). Lots of small flows that might between them add up to reasonable passenger numbers - bearing in mind the track is already there.

 

[MarkyT]

If I've understood this correctly, you're saying that for a Voyager to accelerate once from 50mph to 125mph costs £20 of fuel more than it would cost for that same Voyager to travel that same distance at a constant 125mph. That can't be correct, surely? For a typical car, £20 would buy enough fuel to travel something like 100 miles (complete journey, including all accelerations during the journey and all cruising at constant speed).

When you think of all those truck size engines accelerating vehicles that, in the case of the 221s, weigh nearly 57 tonnes each, it soon adds up. For a 10 car train you're talking around 400 times the weight of a mid-range modern car. The cost of continuing to roll at 125mph will largely be dominated by air resistance alone on level track, plus a small rolling component.

 

[Bald Rick]

If I've understood this correctly, you're saying that for a Voyager to accelerate once from 50mph to 125mph costs £20 of fuel more than it would cost for that same Voyager to travel that same distance at a constant 125mph. That can't be correct, surely? For a typical car, £20 would buy enough fuel to travel something like 100 miles (complete journey, including all accelerations during the journey and all cruising at constant speed).

It’s a rough estimate, and based on a double voyager which I accept are rare beasts on the line at present, but hopefully more common within a couple of years.

190 litres of engines pumping out over 5MW at full chat will burn through a lot of diesel very quickly - about a litre every 2-3 seconds.

 

[DynamicSpirit]

It’s a rough estimate, and based on a double voyager which I accept are rare beasts on the line at present, but hopefully more common within a couple of years.

190 litres of engines pumping out over 5MW at full chat will burn through a lot of diesel very quickly - about a litre every 2-3 seconds.

Thanks! I was still a bit surprised, so I tried approaching the calculation from a different approach - and to my surprise, got about the same answer as you.

I tried reasoning, that a quick Google showed a class 220 Voyager weighs 190 tonnes, so double one is 380 000 kg. And another google turned up that burning one litre of diesel gives you about 36MJ on energy. You want to increase the speed of that mass from 50mph (22metres/second) to 125 mph. And plugging that into the (1/2)*m*v-squared formula for kinetic energy means you need to supply about 490 MJ of energy - which implies burning 13 litres of diesel. I don't know how much the rail pays for its diesel, but at pump prices for cars of about £1.50/litre that does indeed come to about £20. Hopefully there aren't any embarrassing errors in my maths. Since my calculation doesn't take into account friction, air resistance, or the inherent inefficiency of the engine, it would suggest an even higher actual figure.

I am somewhat flabbergasted by how much fuel that takes to accelerate. I am presuming that once the train is up to speed, it doesn't take nearly as much to keep it going for a reasonable distance at that speed?

 

[Bald Rick]

Thanks! I was still a bit surprised, so I tried approaching the calculation from a different approach - and to my surprise, got about the same answer as you.

I tried reasoning, that a quick Google showed a class 220 Voyager weighs 190 tonnes, so double one is 380 000 kg. And another google turned up that burning one litre of diesel gives you about 36MJ on energy. You want to increase the speed of that mass from 50mph (22metres/second) to 125 mph. And plugging that into the (1/2)*m*v-squared formula for kinetic energy means you need to supply about 490 MJ of energy - which implies burning 13 litres of diesel. I don't know how much the rail pays for its diesel, but at pump prices for cars of about £1.50/litre that does indeed come to about £20. Hopefully there aren't any embarrassing errors in my maths. Since my calculation doesn't take into account friction, air resistance, or the inherent inefficiency of the engine, it would suggest an even higher actual figure.

I am somewhat flabbergasted by how much fuel that takes to accelerate. I am presuming that once the train is up to speed, it doesn't take nearly as much to keep it going for a reasonable distance at that speed?

Two errors, which nearly cancel themselves out...

1) the average thermal efficiency of a Diesel engine and electric transmission is in the region or 30-40%, ie that 36MJ of energy per litre of fuel only gives you around 11-14MJ of useful energy to power the train (and all the ‘hotel’ services). So you actually need to burn approx 3 times as much. To quote Captain Deltic, a good rule of thumb for Diesel engines is that about a third of the energy goes up the exhaust, a third goes out the radiator, and a third turns the wheels.

2) current pump price is about £1.05/litre for road vehicles, but about 48p/litre for the red diesel rail can use; ie the cost per litre is about a third what you assume.

So full marks for an approximate correct answer, but a few marks docked for your workings.

Air resistance is also a significant factor.


As an aside, whilst the cost isn’t so large for smaller units and lower speeds, you can see why request stops are a thing.

 

[MarkyT]

Air resistance is also a significant factor.

Air resistance reduces at lower speeds, so the current slow down and re-accelerate no doubt saves a little energy (in that respect alone) compared to a notional 125mph cruise through. I'm sure it's not a significant enough saving to counteract the additional fuel use though!

 

[Bald Rick]

Air resistance reduces at lower speeds, so the current slow down and re-accelerate no doubt saves a little energy (in that respect alone) compared to a notional 125mph cruise through. I'm sure it's not a significant enough saving to counteract the additional fuel use though!

Yes, good point. Although even on ‘tick over’ a double voyager will be consuming a litre every couple of minutes, so the time stationary costs too!

 

[ABB125]

Yes, good point. Although even on ‘tick over’ a double voyager will be consuming a litre every couple of minutes, so the time stationary costs too!

**cough cough** (literally!) Birmingham New Street
I appreciate the need for longer dwells every so often for recovery time, so would it be possible to switch off some of the engines whilst idling to save money?

 

[Kettledrum]

Given Bald Rick's calculations that it would save 1 minute in a journey time with a notional value of £300k pa per non stop train. There must be at least one non stop train each hour in each direction passing straight through, but I don't have a precise figure to multiply the £300k pa with. If it's 20 trains not stopping at Burton a day, this would save £6M per annum, so it is significant. Unfortunately, so would be the cost of building new platforms and re-aligning the tracks at Burton-on-Trent. Foe example, I understand that the recent remodeling work at nearby Derby station was £200M. What would the capital cost of the re-alignment at Burton compare?

 

[Bald Rick]

Given Bald Rick's calculations that it would save 1 minute in a journey time with a notional value of £300k pa per non stop train. There must be at least one non stop train each hour in each direction passing straight through, but I don't have a precise figure to multiply the £300k pa with. If it's 20 trains not stopping at Burton a day, this would save £6M per annum, so it is significant. Unfortunately, so would be the cost of building new platforms and re-aligning the tracks at Burton-on-Trent. Foe example, I understand that the recent remodeling work at nearby Derby station was £200M. What would the capital cost of the re-alignment at Burton compare?

Err - no. It’s about £20 per non-stop train in fuel, if they were all double voyagers (they’re not). But if they were, there’s about 50 trains a day non-stop SX, hence £1000/day. There’s fewer at weekends, and of course there would be engineering works occasionally, so it’s about £300k pa total for all trains, all year.

That’s fuel cost only; there would be some other costs but not much.

If the minute saved could be taken into the journey time, there would be a revenue gain too, but as others have said it is likely that it can’t be taken into the timetable due to constraints elsewhere.

Complete guess, but a realignment with fast lines through the middle and platform loop lines on the outside would be in the region £40-60m.

 

[ABB125]

Complete guess, but a realignment with fast lines through the middle and platform loop lines on the outside would be in the region £40-60m.

Does that include upgrading the goods lines? I believe they are currently limited to 15mph, and may require a signalling upgrade.

 

[Bald Rick]

Does that include upgrading the goods lines? I believe they are currently limited to 15mph, and may require a signalling upgrade.

As I said, a complete guess. But yes it would mean resignalling. All the lines would have to be replaced, and there would be fairly significant signalling changes, particularly to the goods lines (which are only for freight services today, correct).

 

[Kettledrum]

Err - no. It’s about £20 per non-stop train in fuel, if they were all double voyagers (they’re not). But if they were, there’s about 50 trains a day non-stop SX, hence £1000/day. There’s fewer at weekends, and of course there would be engineering works occasionally, so it’s about £300k pa total for all trains, all year.

That’s fuel cost only; there would be some other costs but not much.

If the minute saved could be taken into the journey time, there would be a revenue gain too, but as others have said it is likely that it can’t be taken into the timetable due to constraints elsewhere.

Complete guess, but a realignment with fast lines through the middle and platform loop lines on the outside would be in the region £40-60m.

Thanks for explaining the calculations - it makes a lot more sense now. With such a large discrepancy between the benefits and the costs, surely that means it's unlikely to happen. By comparison, the recent Market Harborough track re-alignment work cost £54M but there was a large amount of additional car parking income that would be generated to sweeten the business case. There are also more non stop trains at Market Harborough, so far more benefits.

Surely the financial case for the work at Burton probably wouldn't stack up?

 

[Bald Rick]

Thanks for explaining the calculations - it makes a lot more sense now. With such a large discrepancy between the benefits and the costs, surely that means it's unlikely to happen. By comparison, the recent Market Harborough track re-alignment work cost £54M but there was a large amount of additional car parking income that would be generated to sweeten the business case. There are also more non stop trains at Market Harborough, so far more benefits.

Surely the financial case for the work at Burton probably wouldn't stack up?

Very unlikely to stack up on its own. The only chance would be if it was done concurrent with a load of renewals (track and signalling) and station works all due in roughly the same time frame.

 

[MarkyT]

Here's an alternative idea to ease the reverse curves at the south end of the platform by the following means.
1. Slew all lines outwards from the alignment centre line for a distance of approx. 400m to the north of Borough Road Bridge. Some land take from adjacent car parks may be neccessary, particulalry on the west side.
2. Construct a new island platform between the realigned fast lines. This would be a long wedge shape gradually tapering down towards the Derby St. E footbridge, north of which existing alignments would be assumed. Signalling changes as required.
3. Operations transfer to new platform, accessed from existing station entrance through openings in existing Borough Road Bridge. Demolition of old platform commences.
4. Once old platform removed, realign fast lines south of Borough Road bridge with gentler curves to allow faster through speed.
This would have the main advantage of keeping the existing track layout largely functionally intact, with no junction and few signalling alterations required apart from possibly replacing some signal structures for clearance and sighting. For freight, in particular, there would be no changes in the area serving the various sidings on either side connected to the loops. Improvements to station facilities, platform length, stepping distance etc could also be included. Maybe 125mph couldn't be achieved, but a considerable improvement on the current 50mph restriction should be possible.