 These were capable of and although not initially equipped to tilt, were designed to be easily upgraded to tilt mode by having trailer profiles that tapered inwards at the top and suitable bogies.Speeds of were tested on the southern, straighter sections of the ECML by using a flashing green aspect on the signals.This indicated it was safe to proceed above , but HMRSI eventually ruled that this was dangerous and that speeds above 125 mph would require in-cab signalling.