Thank you!
Been reading up on it and it sounds like an interesting addition to the metro line if it ever happened. Pelaw - Washington - Durham...
The most common suggestion for using part of the Leamside line in Metro applications would be the transformation of the Sunderland tram-train alignment into a loop; Pelaw, Sunderland, South Hylton, Washington, Pelaw.
Otherwise, the Leamside line north of Chester le Street has been widely proposed as a freight route, reducing pressure on the ECML west of Gateshead. That would then imply a link through Gateshead from the Leamside line to the Team Valley line so as to access the Tyne Yards from the north without interfering with ECML passenger services.
Then again, the Leamside line south of Chester le Street has been proposed as a higher speed bypass for the windy sections of the ECML through Durham city.
It is an interesting speculation how much these various aspirations may be consistent with one another; and if not, who gets first dibs.
On the face of it however, it would be less likely that Metro services would run through the core tunnel; and out to Durham via Washington, as there is limited scope for additional peak capacity to accommodate it. More likely - in my view - would be a reconfiguration of surface level commuter services into Newcastle to use a common Metro replacement stock in longer train formations - e.g triples, like on the DLR. We know that the replacement specification exercise (whose outcome may be published shortly) would envisage the new Metro LRVs to be capable of being fitted with hybrid diesel power - as also 25kv OLE dual voltage, though not at the same time - and that could imply a through-running Metro 'overground' network to complement the current Metro 'underground'.
The Leamside line forms a component of several such plans.