It seems to me paths that are used by freight and local services is cited much as a reason not to implement higher speeds. If ALL Intercity's under the wires could achieve the same speeds then surely faster services frees up paths when using ERTMS
...but we don't have many tracks which are only used by "fast" trains.
Much of the ECML is two (or three) track - I have no figures available, but I'd imagine the four track sections are a minority. There are few flyovers/ grade separated junctions. This means that the "Inter City" services have to share the tracks with the freight trains, the Pacers, the conflicting movements, the flat junctions (Newark).
To give an example, IIRC the southbound sprinter from Grantham to Peterborough (the EMT service from Liverpool) has to cross the northbound "fast" line twice, which cuts the number of paths avaiable.
You can have all the "Intercity" services doing 140, which is fine on a contained stand-alone route, but little use when the freight in front is only going at half that speed.
Nah, for me higher speed is only worthwhile on a dedicated line (like HS2), because otherwise the speed differentials are too significant, and you catch up with the slow trains in front far too quickly.
Instead of trying to turn the ECML into a 140+mph railway, you'd be better starting from scratch with a purpose-built line (like Virgin planned to do on the ECML if they won the bid from GNER, or like HS2)
--- old post above --- --- new post below ---
I wonder how much time getting a Morpeth curve bypass would save? I suspect it would quite easily be 10 minutes, but if it was ever built it would make a good loop for passing freight and local services (should the unlikely Newcastle - Scotland local ever happen).
This was one of Virgin's planned "avoider lines". Personally I think that this would be a better use of resources than trying to increase the line speed elsewhere.
Bypass Morpeth and you have a lovely long "dynamic" loop (since some of the loops on the ECML are only really long enough for freight to sit in, meaning it has to come to a halt, and start up again once the path is free, which is a lot slower than if it could maintain momentum).
You also have the possibility of more local trains serving Morpeth (as you say), because they could do this without occupying the main line.
I think your ten minutes figure sounds reasonable - its a long stretch to slow down for, maintain a slower speed and speed up again - much faster to maintain speed on a new line. The accident with the Sleeper is a reminder of why the Morpeth curve needs to be treated with care.