M4 is one of the major motorways in United Kingdom, London to Bristol and on to South Wales.
This southern east-west motorway passes through fourteen counties: Greater London, Berkshire, Buckinghamshire, Wiltshire, Gloucestershire, Monmouthshire, Newport, Cardiff, Vale of Glamorgan, Rhondda Cynon Taff, Bridgend, Neath Port Talbot, Swansea and Carmarthenshire.
