Investment has gradually spread westwards since the 1980s.[16] In the west, the interchange of the M4 and M5 motorwaysnorth of Bristol had seen considerable growth of industries by the mid 1990s.[17]
The 1980s and 1990s saw the development of the Swansea Enterprise Park.[19] The Celtic Manor Resort, adjacent to the M4 in Newport, has received significant investment[20] and hosted the 2010 Ryder Cup.[21] Newport has seen significant growth in the electronics industry since the late 1980s.[22][23] The 1990s saw significant investment in Cardiff, such as in Cardiff Gate and the Cardiff Bay area.[24] One site of note on the M4 corridor is Port Talbot Steelworks – the largest steel producer in the UK and one of the biggest in Europe.[25]
The opening of the Second Severn Crossing in 1996 resulted in the previous M4 and bridge, serving Chepstow, being renumbered the M48, although the area is still generally considered as falling within the M4 corridor.[26][27]
Since the start of the 21st century there has been evidence of more investment west of Cardiff, such as: