NotATrainspott
Established Member
- Joined
- 2 Feb 2013
- Messages
- 3,223
No it couldn't, both sides of the four track layout west from Haymarket are fully occupied, certainly if you add a station stop at Gateway, and have been for many years. And you can't even four track from Saughton Junction out to the proposed Dalmeny curve as each side of the Fife line at Gyle has been developed right up to the boundary fence.
It's not as bad as that. See, the constraints through Haymarket are more about constraints across the wider rail network. Extra paths are possible through the station, but they then can't be used to run meaningful rail services. For instance, you might have a path available to Linlithgow, but then there's nowhere for a train to get out of the way of the E&G express barrelling up behind it, and even if there were there's not a lot of point running a train that wouldn't go to where passengers want it. These gaps exist on both the north and south lines, and the Dalmeny Chord is a fairly neat way of being able to use them to run more services. First of all, it would be grade-separated at both ends: the new junction on the Fife lines, and the existing Winchburgh junction on the E&G. The new middle junction between the existing Dalmeny line and the new chord to the Gateway doesn't need it due to very low traffic. This means using the new chord incurs very little penalty for capacity on either existing line. Then, you can use a timetable gap on a line, jump onto the chord and then end up in another gap on the other line.
For instance, you could use a gap in the north line timetable heading west of Haymarket to run an E&G express at the same time as a Dunblane stopper runs on the south lines. As the stopper calls at Edinburgh Park and Winchburgh, the E&G could stop at the Gateway (or run fast) and then take the new chord to end up ahead of the Dunblane train. The north lines essentially become a long grade-separated dynamic loop for the south lines, including the flat junctions at Haymarket and Newbridge. Therefore, westbound E&G/Dunblane services don't need to conflict with eastbound Shotts, Carstairs, WCML and Bathgate ones. Trains through Linlithgow can now leave higher-numbered platforms at Waverley without needing to cross over and block the lower numbers. It's not going to magically enable another 10 trains an hour but it's the best enhancement currently available for capacity west of Haymarket.
The chord was originally going to be included in EGIP back when it involved running a 6tph 6-carriage E&G shuttle. When the project was restructured to lengthen the current 4tph to 8 carriages, the chord and the other grade-separation work at Greenhill was no longer required. However, NR have kept them on the back burner as they know they will be needed soon for other improvements and capacity enhancements.