M4. Aust to Almondsbury (J21 to J20)

Richard Costain Ltd were awarded the contract for this 4.5 miles section of motorway at an estimated cost £3 million and commenced work in August 1963. The section was constructed as dual 24ft carriageways to complement the Severn crossing with cycle tracks from the Bridge as far as the Aust interchange. A feature of the length is the additional mile long "Crawler lane" at the approach to the Almondsbury Interchange. At the Aust interchange with the A403 and B4061 a Service Area was constructed by Higgs and Hill Ltd. On this section there are thirteen bridges over or under the motorway and two pedestrian underpasses. Four large Armco steel culverts carry water courses under the road .Over a section of about 1.5 miles the ground below embankment was of poor bearing value and this area was surcharged with ten feet of fill for a period of a year to preconsolidate the ground before construction of carriageway work. Over the whole contract there was a surplus of excavated material amounting to approximately 1 million cubic yards of which 400,000 was used at the Almondsbury site.