The timetables are the least of the issues imo on this type of corridors. The thing that is worse is the numbers being all over the place so people will just let them go anyway regardless as it's a different number totally so 'probably' takes another route.

They really need to assign blocks in particular in Sunderland and try and assign numbers so all the routes along each corridor have a block of numbers.

8/78
2/2A/39/39A/78
60/61/62/2/2A/39/39A
20/35/55/X20

8 = 8
78 = 7
2/2A = 70/71
39/39A = 72/73
60/61/62 = Leave the same
X6 = X60
35/35A = 35/34
55 = 36
20/X20 = Leave the same

Means the blocks would be instead:

7/8
7/70/71/72/73
60/61/62/70/71/72/73
20/35/36/X20

Then you can just say catch the 7's upto every 5 minutes along Chester Road or catch the 60's/70's to Grangetown similar to what everyone does with the 40's in Newcastle to Gosforth or the 60's to Killingworth. I also don't like A's for the sake of it.