There's been a lot of discussion on here about route numbers and how they are in a right mess, and I fully agree! You have the 1 serving North Tyneside mainly but then have the 2 serving Sunderland, the 4 mainly around Washington and Houghton, and then the 5 around South Shields. It's just all over the place. How about something this: -

North Tyneside - 1-50

Gateshead area - 50-100

Consett area - 101-150

County Durham area - 151-200

Washington Area - 201-250

Sunderland area - 251-300

South Shields - 301-350 etc

This is just an example. Ok there may not be 50 bus routes in one area but this would make room for any potential new routes for each area in the future. Routes to major attractions such as the MetroCentre should start with the letter of the main attraction it serves, so the X66 would become the M1 for example. All Xlines would be renumbered but retain the X at the start. Just a thought.