Leamington - Coventry wouldn't get any relief as the route wouldn't go via Coventry. If you want to go south coast - Birmingham and don't care about Coventry then you can already go via the Bordersley curve.
I meant the route in terms of rail traffic, it's not Coventry that is the target, but more capacity on the South Central to WM and beyond axis.
But being relieved by a new pair of lines being built nearby…
HS2 Phase 1 isn't much use for South Central to WM and beyond without a significant detour via London. It will help Stour Valley congestion, but then there is demand for increased suburban services in the WM that will fill a lot of that capacity.
Why build the curve, saving on S&C, signalling etc if its just as easy to reverse at Honeybourne and create the connection by default. Moreton in Marsh is a daft way of doing it. All routes have finite capacity, Bald Rick has answered the Stours issue.
Reversal at Honeybourne is very cumbersome in a line with quite constricted timetabling as it is. Approx. 0.6 mile/1km curve on land unobstructed in the middle of the countryside is going to be a small part of the overall project to deliver, with significant benefits associated with scoping this part of the project.
I'm surprised nobody has (yet) proposed rebuilding the SMJ (Stratford-on-Avon and Midland Junction) line from Fenny Compton to Stratford and running a London/Stratford service that way.....
It's a possibility, but a few thoughts on that proposal:
1) MOD Kineton on current route - would you need segregation from the active munitions depot and what level of segregation?
2) Length - we're talking 14 miles plus, compared to 10 miles Honeybourne to Stratford Parkway (especially to avoid the obstructions which I'll mention next). Although it is important to mention that it is more direct for trains to Stratford from Oxford/London.
3) Some obstruction of the route around Kineton itself (easily diverted around) and significant encroachment on the route closer to Stratford.
1.5 miles of the former alignment into Stratford has been converted to road and the urban sprawl of Stratford's eastern suburbia makes a bypass to join the line from the north at Bishopton/SoA Parkway quite long.
I've drawn a line for the potential bypass/approach in Stratford in the below attached image that is around 6 1/4 miles long, but even that comes with several short tunnels under villages and the edge of golf courses.
Or you could try a tunnel from the end of the unobstructed alignment east of Stratford to Stratford station, but it would be about 1.5 miles and I'm not sure what the ground conditions in the Avon valley are like.
It's not a bad idea overall, but I think you'd need some additional development (e.g. a large housing development near Kineton) to justify it.
