1. Where the sign is a variable message sign which displays the numeral by means of light-emitting characters or symbols in such a way that the sign is only visible when associated equipment detects the presence of a vehicle exceeding the speed limit indicated by the sign, the variable message sign may display, beneath the sign displayed on it, the legend “SLOW DOWN” in characters having a height not less than one quarter of the height of the displayed sign.E+W+S
Commencement Information
I1Sch. 10 Pt. 3 para. 1 in force at 22.4.2016, see reg. 1(b)