tbh if they spent some time actually changing some priorities in Newcastle they could change it so every route would serve the Central Station heading South and also North / East instead of stopping miles away outside the Mile Castle but it would involve changing:

• Changing Neville Street so there's an extra lane heading East by using the space currently loading bays and bus stops (there won't be any West buses anymore)
  
• Reverse The Bigg Market so heads South to North
  
• Reverse Clayton Street so it heads North to South
  
• Reverse Newgate Street so it heads East to West.
  

Once you've made those changes you could route the buses so they do the following routes, the blue services being the Market Street / Tyne Bridge loop services and the red route being the Scotswood Road, West End and Redheugh Bridge routes.

Below are quick diagrams of it.

North / East


South / West


It would help in the Newgate Street / Market Street area aswell with less conflicting flows which should help the buses flow a bit better. Neville Street / Berwick Street would be a gyrotory hence the looping up for the North services.