Potential infrastructure improvements needed to achieve WAG's twenty year plan

[tasky]

Moderator note: split from https://www.railforums.co.uk/threads/welsh-government-twenty-year-plan.192660/

They're not going to be able to achieve these without building some kind of high-speed track from Swansea to London are they? Either a new line or by-passes, and probably a new Severn crossing?

Journey times between Swansea High Street and Cardiff Central to be no more than 30 minutes.

Journey times between Cardiff Central and Bristol Temple Meads to be no more than 35 minutes.

Journey times between London Paddington and Cardiff Central to be no more than 85 minutes.

 

[HSTEd]

Well we do really need a new Severn Crossing.
The current one is hardly fit for purpose.

 

[tasky]

Well we do really need a new Severn Crossing.
The current one is hardly fit for purpose.

Am I right in thinking that maintenance costs on the tunnel are astronomical and that a new crossing could potentially save on them?

 

[HSTEd]

Am I right in thinking that maintenance costs on the tunnel are astronomical and that a new crossing could potentially save on them?

Well it apparently eats electrification equipment with startling speed.

 

[Meerkat]

One of the Severn barrage proposals included a new rail crossing splitting to go both ends of the locks so one of the two lift bridges would always be available.

 

[Tomos y Tanc]

Maybe they'll finally get around to building this!

 

[Rhydgaled]

Journey times between Swansea High Street and Cardiff Central to be no more than 30 minutes.

Blimey that's fast; even Bridgend to Swansea is more than that at present. Rouding up, the current route is 46 miles. The current GWR journey time of 54 minutes is therefore an average speed of just over 50mph, to get it down to 30 minutes would need an average speed of 92mph.

I don't think they specify how many trains need to meet these timings, so enhancements that would only benifit GWR's London services might be compliant with the target. But would a class 800 (in electric mode, let's assume that such a big project would involve or at least lead to electrification) departing Bridgend be able to reach 125mph before having to brake for the Port Talbot Parkway call?

If 125mph is not practical given the spacing between stations, or the 100mph trains on Manchester-Swansea are also required to make the 30 minute target, then the route will need to be shorter. As the crow flies, Cardiff Central to Swansea High Street via Bridgend, Port Talbot Parkway and Neath is 39.05 miles according to Google maps. Even using that clearly impossible route, a 30 minute journey time would require an average speed in excess of 78mph. Is a 78mph average speed over such a distance remotely plausable with three intermediate stops?

 

[HSTEd]

Shinkansen could manage that.
A Class 395 might just manage that but it would need a lot of 140mph running

 

[tasky]

Given the circuitous nature of the current route and the capacity for savings by shortening it, coupled with the fact we've been unable to upgrade any existing line to 140mph yet, it seems likely that a new alignment would be a sensible option to consider

 

[Rhydgaled]

Shinkansen could manage that.

What exactly? 40 miles in 30 minutes with three intermedate stops? Port Talbot to Neath is only (rounding up again) 6 miles on the existing network, what sort of top speed could a electric train reach before having to brake for the next station?

Given the circuitous nature of the current route and the capacity for savings by shortening it, coupled with the fact we've been unable to upgrade any existing line to 140mph yet, it seems likely that a new alignment would be a sensible option to consider

A new alignment between Cardiff and Bridgend seems like the best bet. Bridgend - Port Talbot - Neath is less circuitous and approaching Swansea High Street from any other direction than the current one would be difficult. You could maybe sqeese two through tracks (but only one platform) on an old bit of viaduct which currently seems to be used as a car park along one side of Swansea station, but I'd suggest that one platform wouldn't be enough for fast services. By splitting the platform into two (like A and B sections at other stations, but actually numbered seperately) it might be usable for a Swansea metro though.

But you'd still need to do something quite significant between Bridgend and Swansea to get the journey time down sufficiently.

 

[HSTEd]

What exactly? 40 miles in 30 minutes with three intermedate stops? Port Talbot to Neath is only (rounding up again) 6 miles on the existing network, what sort of top speed could a electric train reach before having to brake for the next station?

Assuming my limited Class 395 dataset is accurate, and assuming the train has the same braking performance as it's accelerating performance.
About 200kph with a 9600m or so stop spacing.
Journey time on order of 4 minutes for an average speed of 90mph.

 

[Meerkat]

What are the speed limit constraints between Cardiff and Swansea?
I can see some wiggly bits that could be straightened out a bit, a fair number of crossings that might need to go, and a fair amount of space for long dynamic loops, preferably including some station rebuilding/movements to get them on the loops.

 

[Rhydgaled]

Assuming my limited Class 395 dataset is accurate, and assuming the train has the same braking performance as it's accelerating performance.
About 200kph with a 9600m or so stop spacing.
Journey time on order of 4 minutes for an average speed of 90mph.

Thanks. I wonder how the class 395 compares to the class 800 which of course is the only type operating on the route in question that could exceed 100mph (unless the class 802s still appear as well). There is an acceleration curve in the IEP Train Technical Specification. Braking requirements appear to be refered to this railway group standard.

Given my earlier estimate of a required average speed of 92mph and your information that a 395 could average 90mph on a short hop, it would appear that as a minimum a linespeed of 125mph would be required throughout unless stops are removed or the route is shortened. If the radius required for 125mph given here (for USA) applies in the UK then the currently alignment appears to be some way off allowing that, so at least some new alignment seems to be a necessity (expect perhaps if the services are non-stop).

 

[tasky]

What's path capacity like on the line? Presumably adding more non-stop services at the same time as intensifying stopping services with the South Wales Metro for a large part of the line is a recipe for using it up, if any exists

 

[Rhydgaled]

What's path capacity like on the line? Presumably adding more non-stop services at the same time as intensifying stopping services with the South Wales Metro for a large part of the line is a recipe for using it up, if any exists

I have an 'Existing Capacity Utilisation' map saved on my PC which I think came from Network Rail's Wales RUS (Route Utilisation Strategy). It shows the Welsh rail network drawn with red, yellow and green lines. Cardiff-Bridgend is red (high utilisation), then yellow (medium utilisation) to Neath, green most of the way to Swansea and red into Swansea. East of Cardiff the four track section is shown with two of the tracks at 'high utilisation' and the other pair of tracks green for 'low utilisation'.

As you say, there could well be a problem with adding additional services west from Cardiff due to the mix of fast and slow trains (there might be freight to consider as well as Maesteg stoppers, I'm not sure how much of the freight goes via Barry versus Pontyclun). One thing that may help in the short term is the new station at Miskin if it is to be built on the existing Miskin freight loop with platforms on the loop lines and not the mains. That would allow the stoppers to be overtaken while they call at Miskin.

 

[option]

Journey times between Swansea High Street and Cardiff Central to be no more than 30 minutes.

Blimey that's fast; even Bridgend to Swansea is more than that at present. Rouding up, the current route is 46 miles. The current GWR journey time of 54 minutes is therefore an average speed of just over 50mph, to get it down to 30 minutes would need an average speed of 92mph.

I don't think they specify how many trains need to meet these timings, so enhancements that would only benifit GWR's London services might be compliant with the target. But would a class 800 (in electric mode, let's assume that such a big project would involve or at least lead to electrification) departing Bridgend be able to reach 125mph before having to brake for the Port Talbot Parkway call?

If 125mph is not practical given the spacing between stations, or the 100mph trains on Manchester-Swansea are also required to make the 30 minute target, then the route will need to be shorter. As the crow flies, Cardiff Central to Swansea High Street via Bridgend, Port Talbot Parkway and Neath is 39.05 miles according to Google maps. Even using that clearly impossible route, a 30 minute journey time would require an average speed in excess of 78mph. Is a 78mph average speed over such a distance remotely plausable with three intermediate stops?

There's no mention on that snippet of any stops between Swansea & Cardiff.
Maybe the thinking is that a GWR service would drop Port Talbot, & possibly Bridgend, & that TfW would have a more intensive local service.

 

[VT 390]

There's no mention on that snippet of any stops between Swansea & Cardiff.
Maybe the thinking is that a GWR service would drop Port Talbot, & possibly Bridgend, & that TfW would have a more intensive local service.

Unless there was another GWR service I do not think the London service missing Port Talbot Parkway and Bridgend would be popular.