(17 Aug 2017, 4:08 pm)Dan wrote It's not so much that the interworking of the 8 and 78 causes an issue, but trying to maintain an even headway on other corridors on the network.
As you rightly suggest, the timetable of the 35/36 needs to be built so that it provides a 15-minute headway on some parts of the route (or as close to a 15-minute headway as possible).
On top of that, the timetable of the 36 is built to provide a 10-minute headway between Silksworth, Barnes Park and City Centre (combined with service 33). The timetable of the 36 is also built to provide a relatively even headway (approximately every 15 minutes) between Chester-le-Street and Great Lumley together with service 78.
There are bound to be more examples, but not every shared corridor can have an even headway, and I think it's a case of prioritising some corridors over others (for example, there is competition between Stagecoach and Go North East on the corridor between Silksworth and the City Centre, so it is more important to maintain an even headway here, rather than to Hylton Retail Park where there is no real competition).
So basically they have a monolopy so GNE don't care!