(30 Jun 2014, 1:54 am)aureolin wrote I'd say the frequency of the 4 is perfect for connecting on the X9/X10 already.
As long as the connection doesn't need to be early in the morning or late evening (commuters) and the furthest south you live on the 4 route is Washington :p
Using the 4 to get to Heworth for a connecting bus to Teesside (arriving before 9) isn't practical or possible for many (myself included).
The return journey can be done, but it is a long journey after being at work.
Seeing the bus whizz past sliproads on the a19 when heading North, being moments from home and knowing you wont be back in the vicinity for circa another 60mins is demoralising too.
Going via Durham on the x1/2 or Sunderland on the train is a lot more convenient and quicker for a lot of people living on the route of the 4 and needing to commute to/from Teesside. Even if it means a change of bus (as much of a pain that is).