I've chanced across some quite detailed diagrams of current Network Rail plans for Oxford, which are in slightly more advanced stages than I've seen before.
Lines marked in black are unchanged.
Lines marked in
red are new sections of track.
Lines marked in
green are sections of track to be removed.
The first one is an overview of the Oxford area. It shows that current thinking is for Bi-Di signalling on both the up and down main lines along with the up passenger loop and an extended down passenger loop as far as just before Wolvercote Junction. Linespeeds on the loops are to be improved massively with the up loop going from 25mph to 75/90mph!
It also shows a re-laid Oxford North Junction for East-West Rail with the current single lead 25mph junction being replaced with a double 50mph junction.
The second one shows the station area itself in more detail. Things to note include the new platform at the back of the current platform 2, with both of those platforms gaining signals so that trains can depart back to London from them. Both bridges at the end of the platforms would be replaced/widened with the line leading to the new through platform meaning the removal of the two 'West Midland' sidings immediately south of the station.
The sidings on both sides are altered to mostly provide for 260m long trains (10-Car
IEP▸ length) and this is achieved by moving the access route into the down sidings closer to the station for two of the three roads which would then not be able to access the current up platform, though with two other London platforms available that would not be a problem. The up sidings would be extended by removing the headshunt at the Banbury end and making four long sidings using space created at that end.
It appears, from the diagram, that the London end bay platform idea isn't included, although passive provision for a fourth through platform linking through to the current platform 3 would be - though that would mean knocking down the concourse!
The other major alteration is for the Evergreen 3 service, which it appears would only use one additional platform (and could also use the current bay platform), and would have no dedicated line to Oxford North Junction but would instead share the main or loop lines that other services would use.
I must stress that these are only provisional plans, and there may be other plans that are totally different, but just as likely to see the light of day. But it's interesting to get a glimpse of what the current thinking is, and if these improvements were to be made there would be a huge leap in flexibility at Oxford.