The power to make regulations with respect to the use of special roads under section 17(2) and (3) of the Road Traffic Regulation Act 1984 (except with respect to special roads generally) lies with the Welsh Ministers so far as they are exercisable in relation to Wales.

In exercise of the above power, the Welsh Ministers make these Regulations which impose a maximum speed limit of 50 miles per hour (instead of the general 70 miles per hour speed limit imposed on motorways by the Motorways Traffic (Speed Limit) Regulations 1974 (S.I. 1974/502)) on the length of the M4 motorway specified in the Regulations.

A full regulatory impact assessment has not been produced for this instrument as it is made for highway safety reasons and it has no impact on the costs of business.