A4

This article is about the British A4. You may be looking for the Northern Irish, Manx or Jersey road with this number.

Route

This is the A4 going under the Clifton Suspension Bridge

Main Article: A4 route

The A4 was the main road from the west of England to London before the coming of the M4. Its route from Avonmouth to London passes through the cities of Bristol and Bath, and the towns of Chippenham, Calne, Marlborough, Hungerford, Newbury, Reading, Maidenhead and Slough. It partly follows the route of the Great Western Main Line.

For more detail on the western end of the route, see A4/Avonmouth - Bath and A4/Bath - Chippenham. For more detail at the London end, see A4/Great West Road. Other sections are awaiting expansion as below.

The London-Bristol trunk road, created in 1936, followed the A4 throughout its route.

A4 individual sections

Queen Square, Bath

• A4/Avonmouth - Bath
• A4/Bath - Chippenham
• A4/Chippenham - Marlborough (awaiting expansion)
• A4/Marlborough - Newbury (awaiting expansion)
• A4/Newbury - Reading (awaiting expansion)
• A4/Reading - Slough (awaiting expansion)
• A4/Slough - London (awaiting expansion)
• A4/Great West Road

History

Chiswick Flyover in 1959

Main Article: A4 history

Unlike fellow single digit Ax roads, the A4 has fewer changes. This is mostly due to the fact that the M4 follows closely to the route of the A4. Also of the other single digit Ax Roads, it is the only one to be extended since classification.

Notable locations and improvements

Hyde Park Corner

Hyde Park corner from the north

Main Article: Hyde Park Corner

At Hyde Park Corner, the A4 takes the main line and it goes under it. This was built in the early sixies.

Chiswick Roundabout

This is the A4/M4 split at the Chiswick Roundabout

Main Article: Chiswick Roundabout

The Chiswick Roundabout is where the A4 becomes the M4. It is also the meeting point of the North & South Circular roads.

Maidenhead Bridge

Maidenhead Bridge.

Main Article: Maidenhead Bridge

The Maidenhead Bridge is the A4's crossing of the River Thames. It is in the town of the same name.

Newbridge

Newbridge from the River Avon.

Main Article: Newbridge (Bath)

The Newbridge in Bath is one of the oldest bridges in Bath. It was opened in 1736.

Opening Dates

Year	Section	Notes
1925	Brentford Bypass	Great West Road. The final section bypassing Brentford was completed and the full 8 mile road, which included the A30 section to Bedfont, was officially opened by King George V on 30 May 1925. It was a 120 foot road with a 50 foot carriageway. One unusual feature of the road was miniature lighthouses at danger spots.
1928	Colnbrook Bypass	Opened on 18 June 1928. The carriageway was 30 foot wide. Contractor was Messrs. J. Cronk and Sons, Brixton Hill and work began in October 1925. Cost £250,000.
1928	Twyford Bypass	The 2.75 mile road was opened on 10 September 1928 by J.H. Benyon, Lord-Lieutenant of Berkshire. Cost £200,000.
1936	Bristol Portway	The 5.2 mile road from Hotwells to Avonmouth was opened on 2 July 1926 by Colonel Wilfred Ashley, Minister of Transport. It cost £800,000, making it one of the most expensive road schemes in the country. The Government contribution was £200,000. It had taken 5 years to build, had average daily employment of 800 and a minimum width of 65 feet. Opened as A36 and renumbered to A4 in 1935.
1942	Cromwell Road Extension	Warwick Road to North End Road (unclassified when open).
1956	Cromwell Road Extension	Cromwell Road Extension scheme New Stage 1: Chiswick Bypass. The 1 mile D3 section from Chiswick Lane to the new roundabout at the Hammersmith Flyover junction was opened on 26 October 1956 for westbound traffic. The eastbound carriageway was opened from the British Grove (just past the County Boundary) on 17 December 1956 by Helen Bentwich, Chairman of London County Council, with the section to Chiswick Lane opening later. Space had been reserved at Hammersmith for the flyover which opened in 1961.
1958	Cromwell Road Extension	New Stage 2: Butterwick, on the east side of Hammersmith District and Piccadilly Station, was opened on 13 July 1958 to complete the gyratory. This part of the scheme included the dual 30 foot carriageways eastwards to Gliddon Road, which may have opened earlier. The further eastward extension was the final stage (excepting Hammersmith Flyover) with work starting in the Autumn. Notices banning loose dogs between Gliddon Road and North End Road came into force in 1959, indicating the completion date then. The sections of Talgarth Road had a complete rebuild. The Hammersmith gyratory was later renumbered to A315.
1959	Newbury Inner Relief Road	Stage 1 - The 1 mile East-West section was opened on 16 March 1959 by Earl of Gosford. Single carriageway. Cost £126,000.
1959	Chiswick Flyover	Opened on 30 September 1959 by the film star Jayne Mansfield. It connected the Cromwell Road extension with the Great West Road and was almost half a mile long. Beneath it, a 400 foot diameter roundabout replaced the former crossroads with the North and South Circular Roads. Each of the flyover's 4 spans was 125 feet long with a width between parapets of 59 feet. Contractor was Alderton Construction Company Ltd., cost £820,000, who stated they had no involvement in its design and that they considered the design out of date with massive retaining walls and vast amounts of infill, a fact denied by the Ministry. It was planned as part of the London to South Wales motorway and it later became part of M4.
1961	Hammersmith Flyover	Opened on 16 November 1961 by Harold Shearman, Chairman of London County Council. Ernest Marples, Transport Minister and in attendance, declared that it "marks a new age in road planning" and that "it is quite the nicest flyover I have seen in the world". The 2,800 yard dual 24 foot carriageways connected the adjacent sections of the Cromwell Road Extension and included the 1,000 yard flyover supported by 15 tapering columns. It involved a new type of prestressed concrete construction with the precast sections "stitched together" with 33 miles of high tensile steel strands. It had 66 miles of electric cable below the road surface for de-icing. Contractor was Marples, Ridgeway and Partners, cost £1.3 million.
1966	Keynsham Bypass	The 2.25 mile dual carriageway was opened on 26 July 1966 by Paul Dean, MP for North Somerset. Cost £1 million.
1971	Theale Bypass	The 1.6 mile dual carriageway was fully opened on 13 December 1971. Bi-directional operation on a single carriageway had started on 4 August 1971.
1971	Calne Inner Relief Road	Curzon Street to Market Hill, a bypass for High Street. Demolition work for the road was to continue after shop closures in May 1970. Shown on October 1972 OS One inch map. It may have opened in 1972.
1996	Batheaston Bypass	2.7 miles from Bradford Road Roundabout (A4) to Gloucester Road, Swainswick (A46). Opened in May 1996 per Transport Research Laboratory document (26 November 1997). The official opening was on 11 July 1996 by John Watts, Minister for Railways and Roads. The environmentally sensitive scheme had to cross River Avon twice. Visual intrusion was minimised by putting 1 mile of the route in a diaphragm-walled cutting. Contractor was Amey Construction Limited, contract price £45 million, total cost £78 million. Part was A46.

Grid References

• Holborn Circus, London: TQ313815
• Avonmouth: ST516785