Unless I'm mistaken, the majority of trains via Bishops Stortford terminate at Cambridge. Assuming four tracks north of the junction, how would you set them up - paired by use or paired by direction?
If money was no object, I think you would just have a complete rebuild of Clapham Junction with split level platforms rather than messing around with a flyover at Balham.
Surely the main conflict is in the Up direction towards Kings Cross as GN has to cross the other lines to gain access to the branch line via Royston whereas towards Cambridge, there isn't so much conflict if any.
That was my thought. How many Anglia trains from the south side of Cambridge are through trains, rather than terminating?
There's 2tph London Liverpool Street to Cambridge North, 1tph Stansted Airport to Norwich, 1tph Kings Cross to Ely, 1tph Kings Cross to Kings Lynn, 1tph Kings Cross to Cambridge and 2tph Brighton to Cambridge to consider, XC start/terminate at Cambridge so not including them nor am I including Freight.
) making the intermediate crossovers unnecessary in normal service.
No thanks to proposing the Midland Mainline and to a extend the West Coast Mainline being converted from pair by use to pair by direction, that is something I hope never gets considered and I can explain why.As changing the pairing of lines in four-track areas is slipping into the discussion, I'd suggest grade separated crossovers between fasts and slows on the MML to replace the ladders at Carlton Road, West Hampstead South, Radlett and Harpenden. Clearly putting full twin track flyovers anywhere between the core entry and Cricklewood is not going to be simple, even with unlimited cash. Squeezing in a single track bidirectional flyover taking off/landing between the slows/fasts it would at least avoid most of the contra-flow conflicts, (i.e. up fast & down slow), easing the slotting into correct paths.
It might be more viable if the tracks were paired by direction rather than use, (bit more cash needed there
The TL/EM working timetable is a work of art, and works well when everything is hunky dory. Random glitches do occur and delays can build making it difficult for the signalling system to feed trains intothe core in the correct order. Generally, it's the EM traffic that takes the delays.
So if this stretch became four tracked from 'South' to 'Central' - the services are already lined up pretty well in terms of bays and through lines.
Fair enough, - the pairing aspect was an adjunct to the main topic of the thread, but the ECML has a different function in the national network as a spine. The MML, is (or at least was), primarily a passenger-carrying route from London (including a very intensive outer suburban commuter provision) with higher density services that require critical interaction between fasts and slows.
Full bi Di arrangements aren't even going to be considered specifically because of the cost it would endure, there's more chance of seeing electrification at Holyhead then bi di signalling even if it is fantasy.
Regards to the ECML, there's been many times on the past that engineering works means both lines southbound are closed and a 3hr rail replacement bus has had to be endured.
I used to commute from Herne Hill, and spent far too much time waiting for trains... It would probably be possible to grade separate the north end of Herne Hill with the loss of a couple of houses, but that would mean no cross-platform interchange and probably a lower speed limit for non-stopping trains, so I'm not sure it would be all that great a solution. Or build a high level viaduct for the Thameslink side, but I can imagine a few objections to that
Only if you do Water Orton as well, otherwise half a job.
You need to grade seperate the line to/from Coleshill, the current set up is daft, though the fouth track between Water Orton to Castle Brom would make a fair chunk of difference.
The problem there is that there is no simple intervention - each permutation of routes there carries 2tph offpeak, so any one flyover (eg Littlehampton towards Arundel, probably the easiest, though I suspect the ground conditions aren't good) only eliminates 2 conflicts per hour.
Each permutation of routes carries 4tph off peak, not two. This because of the Arun Valley services splitting at Horsham.
It really isn't a big deal though, as the termini of Littlehampton and Bognor Regis are so close that any small incoming pathing delay on services heading there can be absorbed in the turnround layover. As long as real-time junction regulation prioritises London, Brighton and Portsmouth bound services, the junctions cope well. The 3 platforms available at Barnham help manage junction conflicts there and are vital for splitting and joining operations. I'd consider adding a handful of extra points in the Ford area junctions to enable some additional parallel movement opportunities, but no way is grade separation justified, not that this thread is concerned with realism!
Sorry, brain fade - I still think of the stoppers going to Littlehampton, which they haven't for years. Yes, that's 4tph. So the obvious thing to do is to separate the Arun Valley-Barnham flow from the others, but I still don't think it warrants flyovers.
So 2tph Brighton - Barnham, 2 Brighton - Littlehampton, 2 Littlehampton - Barnham.
