Fel rhan o'r broses hon, rydym wedi nodi rhai o'r blaenoriaethau allweddol y byddem yn gofyn i'r cynigwyr eu darparu, man lleiaf, wrth iddynt gyflwyno’u hatebion arfaethedig o ran cerbydau.
As part of this process we have set out some key priorities that we require the bidders to deliver, as a minimum, with their proposed rolling stock solutions: