The M48 is a 13-mile (21 km) long motorway in Great Britain, which crosses the Severn near Chepstow, Monmouthshire, linking England with Wales via the Severn Bridge. This road used to be the M4, and as a result is anomalously numbered: as it lies to the north of the M4 and to the west of the M5, it is in the Motorway Zone 5. The M4, M48 and the A48(M) motorway are the only motorways in Wales.

Aust is a small village in South Gloucestershire, England, about 10 miles (16 km) north of Bristol and about 28 miles (45 km) south west of Gloucester. It is located on the eastern side of the Severn estuary, close to the eastern end of the Severn Bridge which carries the M48 motorway. The village has a chapel, a church and a public house. There is a large area of farmland on the river bank, which is sometimes flooded due to the high tidal range of the Severn. Aust Cliff, above the Severn, is located about 0.5 miles (0.80 km) from the village. The civil parish of Aust includes the villages of Elberton and Littleton-upon-Severn.