Is a five minute saving, if that, between London and Cardiff going to help with union connectivity and justify the investment? Improving the speeds in South Wales would be more useful.
But surely on the GWML the train in front is also doing 140 mph ?
Only if it hasn't stopped, and is capable of reaching 140mph. There's rather a lot of freight on the GWML, which will be negatively impacted by raising linespeeds as they will need to be looped earlier to get out of the way (a lot of freights get looped in Challow Loops, and if the following train now catches them up faster, they may have to be held back at Didcot or Swindon instead to avoid delaying the express.)
I don't think it would so much be the speed, but how it's achieved. For those speeds, you'd need in cab signalling, which would allow trains to run closer together.
Although ETCS will allow closer spacing than conventional signalling, you'll still need greater separation between trains at 140mph than you would at 125mph. And headways at the London end of the GWML are already down near 2 minutes, and ETCS won't make junction conflicts magically disappear.
theres alot to be said about building new lines either side from a new line off Stoke Fifford juntion, under Filton Aerodrome and onwards to the Bishton Flyover all as 125mph track?
I mean, if we are just talking best way, and not necessarily the fastest, wouldn't that be electrifying the entire line? Then again, that would have a speed impact since the IETs could run up to 125 on sections where they can currently only run 115 on diesel power.
Where’s that? Currently anywhere the IETs can do 125 on electric they can do 125 on diesel, though they’re much slower to get there past 110 or so.
The line is already electrified through to Cardiff (remember we're talking in the context context of the Union connectivity review) so not sure of the benefits to anglo-welsh traffic of wiring beyond Bristol.
That is the conundrum though isn't it. Spec for now for efficiency and then get grief if 140 ever sees the light of day, or spec for 140 and it doesnt happen and then get grief for over spec.
Wiring Filton - Temple Meads - Chippenham (and on to Weston-s-Mare and even Taunton while they're at it) would enable local services to be turned over to emu operation (better acceleration, quieter, cleaner, potentially more frequent stopping services) - which would probably do far more for the impression of connectivity in one of the areas that would actually notice than shaving a few minutes off the journey time to London would. Service frequency will generally have a much bigger impact on overall journey time than a modest increase in line speed.
The problem is that IETs aren’t faster than HSTs on diesel in that speed range. Also that section is very wiggly, and it certainly feels like it’s the fastest reasonable speed when on the train. Reading to Taunton already has reasonable speeds compared to other routes for the number of trains that use it. It’s only beyond Newton Abbot that it really slows down, but then that is even more wiggly, so I’m not sure much could be gained west of there either.
When 110mph running was introduced, it was the maximum allowed for single-manned (sic!) running - is that still a factor?
You mean like the original ECML bid from Virgin for a high speed railway?
Being cheeky, the current ECML max speed equates to 201kph, which is '200 plus'...
