I can't seem to find any diagrams showing the intended track arrangements post-EWR, though. Do things remain DDUU, or is the plan DU+DU?
Pre-EWR: DDUU
Post-EWR: DUDU
The pre-EWR plan is DD+UU, but I suspect EWR might well change this to be DU+DU, so that any trains can then use the south-facing bays in Cambridge (Central).
It has to change to DUDU regardless of where EWR services terminate or which platforms are used at Cambridge.
I think you'll find there was extra platforms mentioned in the E-W rail consultation documents (on the east side). So, I'm guessing it's highly unlikely that E-W rail would be using platform's 2 and 3 at Cambridge* (unless of course the plan is to shift what currently uses 2 and 3 to the new platforms to free up 2 and 3 for E-W).
Broadly speaking, yes, if EWR services terminate at Cambridge.
* Bearing in mind, the long term plan is to run onto Ipswich etc, which would mean use of a through vice bay platform.
In that case, it is likely that 1/4 would become EWR through northbound with 7 becoming EWR through southbound.
Great Northern stoppers would terminate in 2/3. Thameslink terminates on new platform 9.
Great Northern and Greater Anglia through services use platform 8 northbound and new platform 10 southbound.
This arrangement de conflicts most of the service groups in conjunction with the four-tracking between Cambridge and Shepreth Branch Junction.
does the flare allow for the length of turnback siding required, and does the horizontal alignment (cant) permit the necessary pointwork?
No.
Is this actually part of the long term plan, or is it just something the concerned politicians have mused about?
Both. Not part of current scope, but latest announcement doesn’t preclude future expansion/extension.
Looking back at Network Rail's Cambridgeshire Corridor Study of 2019 this had a base case of 6x4 cars an hour from EWR in to Cambridge. This required 2 12 coach platforms on the east side at Cambridge station.
The 12-car platforms to the east are to allow current services to be shifted across, freeing up western platforms for EWR.
Biggest question is there going to be a new station on the ECML at Tempsford as well as a station for EWR for interchange purposes. Some posts say yeah some seem to say no or am i wrong ?
Detailed design isn’t confirmed yet, but based on discussions with wider industry ECML platforms on the slows are likely (and as a minimum EWR would make passive provision for later installation).
What is somewhat bonkers is that EW rail will run past the eastern outskirts of St Neots with no station - but you can blame that on St Neots' councillors, if the post upthread on this is accurate.
Adding a station there wouldn’t unlock any specific housing.
If some future developer wanted to pony up the cash (to support a new housing development) then the current design wouldn’t preclude an additional station being added later (the same as for Toft/Comberton).
And I wouldn’t recommend approaching this matter as if the views of St Neots town councillors carry any significant weight in the decision-making - it’s not a plebiscite!