Huckbody Environmental provided oversight and technical advice to ARUP, on behalf of the National Assembly for Wales, as part of the EIA for the proposed motorway scheme. Inputs included review of the design and EIA work undertaken for the Public Inquiry and guidance on minimising the adverse environmental effects during construction.

The M4 motorway links south and west Wales to England and forms a part of the Trans-European Road Network (TERN) connecting the Republic of Ireland and Wales to the rest of Europe. It is an important part of the strategic highway network within Wales.
The National Assembly for Wales proposes to relieve the M4 between Magor and Castleton from the anticipated effects of increased traffic by the construction of an M4 Relief Road.The distance between Magor and Castleton is approximately 25km (18 miles).The existing M4 over this length is a predominantly two lane motorway and it is proposed to relieve it with a new three lane motorway and a new crossing of the River Usk south of Newport.