The A48(M) is a motorway in Wales that links Cardiff with Newport. It is a spur of the M4 motorway. At St Mellons, it runs continuously into the dual-carriageway A48, which also has (albeit narrow) hard shoulders. The A48(M) has no other junctions and opened in 1977. The M4 was extended west from junction 29 in 1980.
Junctions
{| class="wikitable" border=1 cellpadding=2 style="margin-left:1em; margin-bottom: 1em; border-collapse: collapse;"
|+A48(M) motorway junctions
|-
! North-eastbound exits
! Junction
! South-westbound exits
|- align="center"
| M4<br />London
| J29 M4 (Castleton)
| Start of motorway
|- style="text-align:center;"
| Entering the City and County Borough of Newport
|
| Entering the City and County of Cardiff
|- style="text-align:center;"
|Start of motorway<br />Newport
| J29A (St Mellons)
| A48 Cardiff
|}
Previous A48(M) motorways
The Port Talbot bypass which opened in 1966,