Where a constable is for the time being engaged in the regulation of traffic in a road, or where a traffic sign, being a sign of the prescribed size, colour and type, or of another character authorised by the Secretary of State under the provisions in that behalf of the Road Traffic Regulation Act 1967, has been lawfully placed on or near a road, a person driving or propelling a vehicle who—
shall be guilty of an offence.
A traffic sign shall not be treated for the purposes of this section as having been lawfully placed unless either—
and where the indication mentioned in paragraph (a) of this subsection is of the general nature only of the prohibition, restriction or requirement to which the sign relates a person shall not be convicted of failure to comply with the indication unless he has failed to comply with the said prohibition, restriction or requirement.
For the purposes of this section a traffic sign placed on or near a road shall be deemed to be of the prescribed size, colour and type, or of another character authorised as mentioned in subsection (1) above, and (subject to subsection (2) above) to have been lawfully so placed, unless the contrary is proved.
It shall be lawful in Scotland to convict a person of a contravention of this section on the evidence of one witness.