Oxford Corridor Capacity Improvements

What this Phase 2 Corridor works do is give us the new platform 5 - by replacing/adding to the Botley Road bridge and demolishing part/all of the Youth Hostel. That (as others have mentioned) gives the flexibility to bring a terminating train into platform 4 and then a through service (or indeed another terminating service) can be routed into platform 5 without having to wait outside for platform 4 to become clear. That also means that any freight can also get a clearer run through the station heading northwards.

Terminating trains then can, and I suspect often will, turn back in the platform so there will be no need to shunt into the down carriage sidings. That in itself relieves the pressure on shunt moves north of the station and the flow of trains through platform 3. I don't think there will ever be a platform 6, but as and when the station is rebuilt, the option to turn bay platform 2 into a through line should, and probably will, take place. The big thing for me is that this gives us the much needed platform 5, without having to wait until the station building is replaced - which I predict will drag on for many, many years.

Regarding Wolvercote Junction, it would be very nice to have four tracks running up to the junction so that maximum flexibility is available, but that would involve widening, replacing the Duke's Cut bridge - and there isn't a bottomless pit of money. As it is currently, freight and passenger trains tend to wait to be funnelled through that two track station in the northbound direction which is far from optimal and can lead to delays to trains getting onto the Cotswold Line. However the phase 2 works, removing the two AHB level crossings, does make this much better in that the signalling sections are much shorter and trains towards Tackley won't have to wait until the one in front has passed OD2437 before they can proceed.

It would also be nice to have four tracks running south as far as Kennington Junction (some have also said Radley, or even Didcot, but I can't see too much likelihood of that given that it doesn't offer much value to go to just before Radley and would be very expensive to go beyond to Didcot), but again I suspect that is prohibitive on cost grounds.

Other improvements include a much faster route onto the Down Bletchley at Oxford North Junction, meaning that Chiltern services will not have to slow down to 25mph for the crossings onto the Down Bletchley when routed out of platform 4 (and, when built, platform 5). There's only a few such movements today (basically a handful of peak trains that don't fit into one of the bays), but with East-West Rail services, and Chiltern likely to extend along the Cowley Branch, that will be critical.