The Avenue looks a Nightmare for Parked Cars from looking on Google Maps so that would be a big no no, so it would therefore have to go up Harras Bank as you mentioned or Alternatively the B1288/Birtley Lane and then up Fell Bank, I have a feeling it may do the current 83 route into Birtley and up to Northside then back out via Portmeads and Barley Mow Estate.
So therefore the Route could be, Vigo Lane - A167/Durham Road - Sanders Gardens - Blackfell Way - Northside - Portmeads - Barley Mow Estate - Vigo Lane, So basically a One Way Loop of Birtley omitting Fell Bank
RE: Go North East: Upcoming Service Changes