(23 Aug 2017, 3:59 pm)Dan wrote Go North East's Streetlites seem to cope fairly well on long-distance and demanding routes? The 8/78 and 20/20A/X20 spring to mind as being the most demanding.

I don't profess to be completely familiar with the services at Darlington, but I can't imagine them being too dissimilar from the aforementioned Go North East services?

(23 Aug 2017, 4:04 pm)mb134 wrote Was thinking more in terms of the ones based at Ashington. I've been on a Streetlite operated X18 (418) before, and it struggled for a good amount of the route.

I'd say that the X26/X27 & X75/X76 are somewhat similar in terms of demands for routes although the X66/X67 are a bit more duel carriageway road blastings, the Middlesbrough - Saltburn stretch of the X3/X4 routes would probably be a better comparison and whilst the StreetLite's can sit at 50mph easily enough,  I think you would maybe have to add a little bit of extra running time to these services to ensure that they have enough running time, even the worst Omnicity's branded for the X66/X67 allocation can manage about 55mph, so I think a bus limited to 50mph may not be the best fit, EcoCity's manage 52mph, unsure about E200 MMC's but think it may me more than both of them? 

One thing I will say about both demonstrators, just because they are trialing them, doesn't necessarily mean any will actually be purchased, no Optare Versa's or Mercedes Citaro's were purchased for Arriva North East after trials at North East depots in the past.