|Length:||8.4 miles (13.5 km)|
|Meets:||A4, B4064, B4055, M48, B4461|
|Route outline (key)|
The A403 runs along the English side of the Severn Estuary, northwest of Bristol.
It starts in Avonmouth at a major roundabout which is also the start (or end depending on your point of view) of the A4 to/from London. This area is completely industrial and the road travels north as a 4-lane single carriageway past St Andrews Road station.
The road narrows and weaves in and out of the industrial area past various factories belching out smoke and finally leaves all this behind as it travels parallel with the Severn Estuary offering a view to the left of the modern Second Severn Crossing carrying the M4. A road off to the left takes you to Severn Beach; a bit further on a Severnside business Park is accessed on the right.
The A403 then crosses a new bridge over the modern M49: a recent motorway providing a short cut from the M5 to the M4 and vice versa. The main road becomes a dual carriageway for a short while as it goes through the Pilning light-controlled junction where the B4064 from Severn Beach and Redwick and the B4055 from Cribbs Causeway meet.
After this, the M4 is crossed and the A403 traverses a flat marshy plain with the occasional section of dual carriageway at the junctions for Northwick and Old Passage (where the old Aust ferry used to take cars across the river before the first Severn Bridge was constructed). This stretch used to be a continuation of the B4055 before modernisation and upgrades. The A403 ends near Aust at junction 1 of the M48 (ex M4), giving access to the old bridge over the Severn to Wales and also to Severn View services.