Part III of the Transport Act 2000 (“the 2000 Act”) authorises the Secretary of State to make a trunk road charging scheme in respect of roads for which the Secretary of State is the traffic authority, and which are carried by a bridge, or pass through a tunnel, of at least 600 metres in length.
Link: The M4 and M48 Motorways (Severn Bridges Charging Scheme) Order 2017
Source: Legislation .gov.uk
