(01 Feb 2021, 11:32 am)reymyster9 wrote Have they done this for routes beginning with a letter such as the Ventures and X-lines?

I hope GNE would have some common sense not to do that. There would be a lot of confused passengers hoping to get on a 20 or 21 but getting the express version instead. Combined with the route number being on the offside would mean that the "X" is even harder to see. Both X20 and 20 use Streetlites most of the time, quite a few that are in corporate livery on both routes. Similar example on the X21/ 21, both of them (supposed) to be using Streetdecks or B5TLs (Average passenger can't tell the difference). The looks on peoples faces as they speed past Birtley would be quite something!! 

I'm pretty sure GNE wanted to promote the "express" side of the route to stand out so reducing the X wouldn't really help anyway.