The
M4 is a
motorway which runs between
London and
South Wales in the United Kingdom. Major towns and cities along the route include
Slough,
Reading,
Swindon,
Bristol,
Newport,
Cardiff and
Swansea. Originally referred to as the London-South Wales Motorway, the English section, including a
suspension bridge over the
River Severn, was constructed between 1965 and 1971; the Welsh element was completed in 1993. A new Severn bridge, known as the
Second Severn Crossing, was opened in 1996 with the M4 rerouted to use it.