Dave wrote: ↑
18 Aug 2019 16:47
I’m not that clever!
Sad to see Virgin disappear, and worried about First...
Apart from Class 800 seating... I can't say anything bad about First.
They were always fantastic when I worked for them and although their reputation was pretty low, they were steadily getting better and always trying
Here's one for you railwaymen here... something I have often pondered.
Your typical mainline consists of 2 fasts and 2 slows. Either it be in a US/UF/DF/DS formation or US/DS/UF/DF formation.
Most of the time, a fast line will be upwards in the region of 125mph, and slow lines are more often than not 75mph max. Sometimes 80mph in a couple of areas.
Now.. why is that. Why are slow lines so... 'slow' in comparison. This has puzzled me more and more in locations where the geometry is the same as fast lines, track infrastructure is the same too. 3 aspect signalling I could consider, but there's locations where there are 90mph line speeds on 3 aspect signals and just 2 lines.
I wondered, "Maybe the slow lines have to be a percentage under the fast?" But then there are areas of line where the slows reach 80mph, the fasts still remain at 110-125mph. And of course places where the slow line speed remains at 75 whilst the fast drops to 100. So it can't be that either.
So gentlemen, and Dave, I ask upon you if anyone has any idea to this as it is really bugging me at the moment! Obviously you wouldn't expect slow and fast lines to be the same speed. But it's so strange when slows have some kind of a limit of about 75 when running next to a 125 line, but then branch off onto another route and suddenly raise to 90
These are the thoughts that pester me on breaks and also when stuck at reds!