OK here's my plan. Be warned: it's a bit ambitious.
Take trains from Boston/Preston (and further) to the airport through Man Vic instead. Turn right at Miles Platting Junction and right again at Philips Park Junction. Build a new viaduct from the line starting at Philips Park Junction over the line between Ardwick and Ashbury's, to meet the viaduct between Man Pic and Longsight. At this point, the viaduct supports 6 tracks@ 4 in passenger service and 2 accessing Longsight Depot.
View attachment 73151
This is a slightly longer route, but not by much. I doubt that 2.2 miles is going to make a massive difference to demand from the NW of Manchester.
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Supports for the new flyover would be adjacent to the piers of the existing viaduct. The new piers would be tied into the existing for stability. This would also limit the effects of the works on the adjacent landowners.
View attachment 73152
(I haven't shown the foundations for the new piers in the Section C-C away from piers, but these could be there and not affect the use of the land, as these would be underground.)
Speaking of landowners, there is a container yard to the NE of the Man Pic - Longsight viaduct (unfortunately I don't know its name). Even with mitigation, some land would be lost to the owners. However, there is a car park to the north of this site used by the office block on Devonshire Street. If the contractors for this scheme were to build a multi-storey car park for the office block, the land to the NE of the railway could be transferred to the container yard and their land loss mitigated. (complicated - yes I know!)
This scheme also includes a flyover, so that trains to/from Preston can access Philips Park Junction without clashing with other services to/from Stalybridge (eg Transpennine). This would utilise some of the existing railway land to the north of the Manchester-Rochdale line. As far as I can see, this flyover would be wholly on NR land.
In addition, bring back the disused viaduct NW of Deansgate Station. Shift the Metrolink to this viaduct and have a connection to the heavy rail line from Warrington on the (now) vacated Metrolink viaduct. Put two terminating platforms for Deansgate Station where the Metrolink platforms currently are (along with two Metrolink platforms in their new place). Note, if any trams are currently terminating at Deansgate and 3 platforms are required for terminating trams, then Cornbrook (one stop SW of Deansgate) would still be available for this.
Obviously untangle the lines around Salford Crescent (separate services to/from Preston and Southport), and between the Ordsall Chord and Man Vic. (This is shown in the first pic above.)
Some of the results from this:
- Trains between Preston and the airport are taken out of the Castlefield corridor.
- Trains between Southport/Eccles and the airport can be split (if needed) between the Castlefield corridor and the new route through Man Vic.
- Trains between Yorkshire and the airport can be split (if needed) between the Castlefield corridor and the new route (albeit with a reversal at Man Vic).
- Terminating some trains from Liverpool via Warrington will remove some of the Congestion on the Castlefield corridor. Extra services could be provided without worrying about Man Pic Platforms.
- This raises the possibility of a heavy rail station serving the SportCity area (Man City's ground, the athletics stadium and the velodrome).
I told you it was ambitious!