Faster London to Cornwall services

[Sir Felix Pole]

How easily could the Royal Albert bridge bottleneck be mitigated? Obviously double tracking is a very expensive ambition currently, but if it were possible to raise the line speed from its 15mph restriction, and/or reposition Saltash station if this has an impact on bridge utilisation, then capacity could imimprove.

It was double-track right up to the bridge on the Devon side but singled back to St. Budeaux (FRd) to save a bridge span over the SR line in the '70s - this would be the place to start.
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[MarkyT]

It was double-track right up to the bridge on the Devon side but singled back to St. Budeaux (FRd) to save a bridge span over the SR line in the '70s - this would be the place to start.
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That would shorten the single line over the bridge by around half a mile, half it's current extent, and improve standage clear of the Gunnislake branch junction*, little more than the length of the platforms at St Budeaux today. In both directions, signalling has delayed yellow Warning routes for approaching the signals protecting the single line with restricted overlaps clear of the turnouts. This ensures an up arrival at Saltash can be made while a down train is proceeding across the bridge for example. Such a short section of single line, if practically unavoidable, can be managed effectively by a little pathing time added to the timetable. Clearly that wouldn't work on a really busy railway but Cornwall is not exactly London commuter territory.

* Edit 25/8 : On the down the standage is just over 500m for a main line train standing in St Budeaux Ferry Rd clear of both the single line over the Royal Albert bridge ahead and the branch junction behind. On the up its much tighter at around 200m so the tail of a long IET would still be blocking the single line if stopped in the platfrom for any reason. Clearly signallers will know this restriction and try to avoid such a combination of movements if it blocked in a train waiting on the down line for the single line on the Devon side, but it's bound to happen occasionally, especially in event of train or infrastructure failures or late running. Lengthening this section of double track to finish as close to the bridge as possible would be a good project to improve throughput, flexibility and reduce operational performance risk. I wonder if that 70s bridge span over the Southern is approaching renewal any time soon...

Edit 25/8-2 : Looking at photo sources, the remaining bridge is unlikely to be a 1970s structure, being an arch truss design. Old maps suggest the double track here was carried on two separate structures over the LSWR. It looks like the 70s work was to remove another span alongside formerly carrying the down line, maybe an earlier original structure, leaving the current arch truss, later but still old. A signalling record society diagram depicting the layout in 1908 already shows double track at the bridge so the remaining span may be over a century old. I'm not saying there's anything wrong with it at that age and it may well be able to carry on for another century or two with good care and maintenance. However, if there's a desire to change the location of the single to double transition then it might be worth considering replacing it early with a modern span for lower maintenance costs in the future. Then it's a fairly modest upgrade for the bridge alone to carry two tracks instead of one, although clearly to implement a scheme there's the cost of the additional track, wider earthwork and other structure refurbishments, signalling etc. For signalling, although much lineside equipment would be new, the interlocking and signalbox elements could be relatively unchanged as the new turnout position would look exactly like the old one to the system and control panel (I'd change the restricted overlap to a full one clear of the new junction position though with the warning route on approach upgraded to a main, a fairly small change).

Or perhaps more utilisation of existing passing loops, such as more trains skipping Totnes if this is possible. Also resignalling Castle Cary-Cogload junction to a higher signal aspect, so fast trains don't catch up to a semi-fast traversing the long block between just beyond CLC and Somerton.

Totnes is often suggested as a candidate for missing express calls to save time. Operators are not keen on this as the station consistently proves a lucrative source of revenue for long distance travel due to the popularity of the trendy town and its South Hams hinterland with London arts and media professionals, among others. Practically, timing an overtake there would require a long dwell for the stopper, possibly up to ten minutes, due to the long block sections on approach.

 

[Sir Felix Pole]

Yes, the bridge over the SR(LSW) line at St. Budeaux had two separate parallel spans - at slightly different heights to ease the gradient for down trains - singling the line allowed one to be removed. I think they were contemporary, dating from when Weston Mill Viaduct was rebuilt rather then when the LSW line was opened in 1890.

 

[Meerkat]

i just really fancy a high(er) speed and electrified line from Newton Abbott to Plymouth (via Totnes), via upgrading/realigning and Major engineering, but it would be expensive and unpopular with the greens and NIMBYs (personally I love a big viaduct across a valley….)
Apart from the above mentioned decreasing of the Saltash singling I can’t see anything pricey being justifiable west of Plymouth - not a big enough market and all the stations are important.

Isn’t the elephant in the room that speeding it up would increase custom and there isn’t the capacity East of Reading?

 

[Meole]

The air service from Gatwick provides the faster service for those that need it, the expensive rail upgrades cannot be justified as vfm.

 

[stevieinselby]

With electrification, could you increase line speeds 70/75mph to 85/90mph and add some passing loops to shave half an hour off the total London - Penzance time?

It isn't the lack of electrification that keeps the linespeed to 70/75mph – if that was the case then the HST would never have been developed.
The line beyond Newton Abbot is typically limited to speeds below 70mph because it weaves its way through hilly countryside on a twisty alignment. Any work to increase the linespeed would likely involve a lot of heavy-duty civil engineering, and long closure periods while the track is realigned or rebuilt. The payback period for that would be measured in centuries, because there is no alternative route and so a prolonged closure would have a hugely negative impact.
What electrification could achieve would be to allow trains to accelerate faster away from station stops, red signals or speed restrictions (and potentially brake quicker if they could be upgraded to EMUs), which could shave a few minutes off but not a huge amount.

Realistically you've got more chance of speeding up the route between Reading and Exeter than you have between Exeter and Penzance – and you would probably benefit more passengers that way as well.

 

[Devonian]

Totnes is often suggested as a candidate for missing express calls to save time. Operators are not keen on this as the station consistently proves a lucrative source of revenue for long distance travel due to the popularity of the trendy town and its South Hams hinterland with London arts and media professionals, among others.

Indeed, and to quantify "lucrative source of revenue": if a quick look at railwaydata.co.uk is right, about 25% of tickets from Totnes station are to London and the South East, and the station accounts for over 40% of all the tickets to London and the SE from Totnes, Newton Abbot, Torquay and Paignton combined; about the same proportion for the reverse flows.

Totnes is seen as a speck on the map - ironically thanks to the railways taking away its lucrative river trade - but it is the railhead and rail/bus interchange for the majority of folk in the South Hams, even ones not in the arts and media, and has long been an Intercity station for good reason.

Realistically you've got more chance of speeding up the route between Reading and Exeter than you have between Exeter and Penzance – and you would probably benefit more passengers that way as well.

I agree: though eventually a faster coast-avoiding line to keep line speed closer to 100mph as far as Newton Abbot might be slightly more achievable/valuable than straightening the line further west.

 

[HamworthyGoods]

Agree. The 1203 all summer has been London, Exeter, Plymouth and has been very busy when I've worked it. 3 or 4 fast trains a day would give those making the very long trip to Cornwall a choice at least. Sadly the 1203 becomes a "stopper" again next month.....

It’ll be back again next May!

Both the 10.03 and 12.03 are ‘3 hour fast trains’ to Plymouth already, either being fast Reading to Exeter or Paddington to Exeter.

 

[Meerkat]

I agree: though eventually a faster coast-avoiding line to keep line speed closer to 100mph as far as Newton Abbot might be slightly more achievable/valuable than straightening the line further west.

I concentrate on Newton Abbott to Plymouth due to the gradients

 

[stevieinselby]

I agree: though eventually a faster coast-avoiding line to keep line speed closer to 100mph as far as Newton Abbot might be slightly more achievable/valuable than straightening the line further west.

This is the terrain inland from Dawlish. One thing you'll notice it is absolutely full of is contour lines. The only way you're building a new line from Exeter to Newton Abbot avoiding the coastal section is to blast a 12 mile tunnel in a straight line right underneath those hills. And the economics of doing that to save about 6 minutes for fast trains, while still keeping the coastal route active for local services, would be absolutely laughable.