Aside from how it gets built, its interesting that this scheme will potentially drastically cut the journey times from the Sunderland stations to the West of the city centre, if passengers travel via Washington rather than via Seaburn. From the current 39 minutes from South Hylton to around 25 minutes.
Next step surely would be to adapt the Boldon New Curve to Metro running, to allow a South Shields to Sunderland service/loop, likely onward to Washington, but how do you then get it running then onto South Shields again?
A flyover at Pelaw?
Complicated junction/crossing at the top of the bank at the existing Pelaw junction where the South Shields/Sunderland services currently divert?
Reversing at Pelaw?
Or, if you want to spend a bit more money, at the North end of the Leamside, create a East facing junction adjacent to Wardley, utilising the old alignment of the Pontop and Jarrow Railway, now the Bowes Railway Path. The new route can then rejoin the DCL West of Fellgate station in the area of the B1306 Mill Lane and Monkton Business Park, allowing direct running back to South Shields after Brockley Whins via Boldon West Curve.