M4 corridor bridge, serving Chepstow, being renumbered the M48, although the area is still generally considered as falling within the M4 corridor. Since the start of the 21st Century there has been evidence of more investment west of Cardiff, such as: M4 corridor The M4 corridor is an area in the United Kingdom adjacent to the M4 motorway, which runs from London to South Wales. It is a major high-technology hub. Important cities and towns linked by the M4 include (from east to west) London, Slough, Bracknell, Maidenhead, Reading, Newbury, Swindon, Bath, Bristol, Newport, Cardiff, and Swansea. The area is also served
M4 relief road M4 relief road The M4 relief road is a proposed motorway south of the city of Newport, South Wales. Originally proposed in 1991, the scheme was dropped by the Welsh Government in 2009 when costs had risen to £1 billion. They were revived in 2011 with indications of support from the Treasury given in April 2013. There was controversial media speculation that it would be the United Kingdom's second full toll-paying motorway. In July 2014, the Welsh Transport Minister, Edwina Hart, stated that the scheme, following the so-called 'black route', would go ahead and could be completed by 2022. A