The A48(M) motorway in Wales links Cardiff with Newport. It is a 2-mile (3.2 km) long M4 spur. 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.[1][2] The M4 was extended west from junction 29 in 1980.[3]
A48(M) | ||||
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Route information | ||||
Maintained by South Wales Trunk Road Agent | ||||
Length | 2.0 mi (3.2 km) | |||
Existed | 1977–present | |||
Major junctions | ||||
Northeast end | Castleton, Newport | |||
J29 → M4 motorway | ||||
Southwest end | St Mellons, Cardiff | |||
Location | ||||
Country | United Kingdom | |||
Counties | Gwent, South Glamorgan | |||
Primary destinations | Cardiff | |||
Road network | ||||
|
A48(M) motorway | ||
North-Eastbound exits | Junction | South-Westbound exits |
M4 London |
J29 M4 (Castleton) | Start of motorway |
Entering Gwent | Entering South Glamorgan | |
Start of motorway Newport |
J29A (St Mellons) | A48 Cardiff |
The 6-mile (9.7 km) Port Talbot bypass which opened in 1966,[2] was numbered A48(M) before its incorporation into the westward extension of the M4 in the 1970s.[4] Some maps show the Morriston bypass section of the M4 as also having been originally numbered A48(M), although whether this number was ever used on the ground has been questioned.[5]