(02 May 2022, 9:32 am)L469 YVK wrote But why have Arriva used them as their choice of vehicle on the Ashington & Alnwick 'X' routes? The E400 classics allocated to the X15/X18 have done well although well overdue for replacement now given the nature of their work, and they're about to receive 19x E400MMC.

The Ashington express routes (bar the X21/22) are arguably much more demanding than the GNE X21 - the X14 up at Thropton is very hilly, the X15 is constant foot down on the A1, the X18 is rural NSL roads virtually the entire way combined with A1 flogging north of Belford, and the X20 is a combination of the X15 and X18 in that it's constant foot down for the southern section and NSL country roads north of Ashington. 

Aside from this being more demanding than the GNE X21, there was no B5TL available when they first started gaining E400s and at this point fleet standardisation is probably reasonably important.