In the original 1922 road numbering list, the A4 ended at the junction between George Street and Milsom Street in Bath.
On 1 April 1935, it was extended over the A431 and B4044 to Newbridge, and the A36 to Avonmouth.

From Queen Square, Bath, the A4 carries on to Queen Square Place and Charlotte Street, before heading along the Upper Bristol Road by Royal Victoria Park to Newbridge Road.
The road crosses the River Avon on its way to join the A36 and becomes a dual carriageway again until the roundabout that forms the junction with the A39 Wells Road at the Globe Inn and exit for the nearby Bath Spa University.
It continues on through the village of Saltford towards Keynsham where a roundabout splits the road and the A4 continues as a dual carriageway by-passing the town, crossing over the River Chew in the process.

The end of the by-pass coincides with the junction of the Avon Ring Road, the A4174.
The route goes through the suburb of Brislington, going past Arnos Court Park and Arnos Vale Cemetery.
The road runs over a bridge over the New Cut and into Temple Gate where Bristol Temple Meads railway station is located.
The A4 no longer has a defined route from this point to the start of Anchor Road at The Centre; originally it went along Victoria Street and Baldwin Street before turning left onto St Augustine's Parade or, later, Broad Quay, but in more recent times it followed Redcliffe Way, via Redcliffe Roundabout (junction with the A38) across Queen Square to The Centre.
 From there it turns back towards Bristol Harbour via Anchor Road past the We The Curious science museum.
 After another roundabout the A4 follows along Hotwell Road and around a one-way system that merges the A4 with the A3029.

At this point the A4 regains trunk road classification and passes under the Clifton Suspension Bridge along the Portway.
It heads out of the city into the suburbs of Sea Mills and Shirehampton before going under the M5 to end at the roundabout that feeds the motorway, the M49 and A403 in Avonmouth.
In the original 1922 road numbering list, the A4 ended at the junction between George Street and Milsom Street in Bath. On 1 April 1935, it was extended over the A431 and B4044 to Newbridge, and the A36 to Avonmouth.
From Queen Square, Bath, the A4 carries on to Queen Square Place and Charlotte Street, before heading along the Upper Bristol Road by Royal Victoria Park to Newbridge Road. The road crosses the River Avon on its way to join the A36 and becomes a dual carriageway again until the roundabout that forms the junction with the A39 Wells Road at the Globe Inn and exit for the nearby Bath Spa University. It continues on through the village of Saltford towards Keynsham where a roundabout splits the road and the A4 continues as a dual carriageway by-passing the town, crossing over the River Chew in the process.
The end of the by-pass coincides with the junction of the Avon Ring Road, the A4174. The route goes through the suburb of Brislington, going past Arnos Court Park and Arnos Vale Cemetery. The road runs over a bridge over the New Cut and into Temple Gate where Bristol Temple Meads railway station is located. The A4 no longer has a defined route from this point to the start of Anchor Road at The Centre; originally it went along Victoria Street and Baldwin Street before turning left onto St Augustine's Parade or, later, Broad Quay, but in more recent times it followed Redcliffe Way, via Redcliffe Roundabout (junction with the A38) across Queen Square to The Centre.  From there it turns back towards Bristol Harbour via Anchor Road past the We The Curious science museum.  After another roundabout the A4 follows along Hotwell Road and around a one-way system that merges the A4 with the A3029.
At this point the A4 regains trunk road classification and passes under the Clifton Suspension Bridge along the Portway. It heads out of the city into the suburbs of Sea Mills and Shirehampton before going under the M5 to end at the roundabout that feeds the motorway, the M49 and A403 in Avonmouth.
A4 road (England)