A420 road

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The A420 is a road in England that runs from Bristol to Oxford. Since the M4 opened in the 1970s, it exists as two sections.

Western section: It starts on Old Market Street in Bristol city centre, goes through Kingswood, and heads east toward Chippenham. It runs to the north of Bath and into Wiltshire.

Eastern section: It begins at the A419 east of Swindon, goes under the Great Western Main Line at Acorn Bridge, then past Shrivenham and Watchfield to Faringdon. A bypass around Faringdon opened in 1979, and another bypass near Folly Hill crosses the A417. The road then climbs along a limestone ridge that marks the Vale of White Horse, passing Littleworth, Buckland and Longworth. A dual carriageway bypasses Southmoor and Kingston Bagpuize on the way to Oxford.

Most of the Swindon–Oxford stretch is 50 mph, except where there are dual carriageways and a short section near Faringdon. A dual carriageway near Cumnor Hill gives a view of Oxford from the west. After crossing the Oxford Ring Road, the A420 goes through Botley, then onto Botley Road, crosses the River Thames on Osney Bridge, and reaches central Oxford near the station. In Oxford it follows Oxpens Road, Thames Street, parts of St Aldate’s and High Street before climbing Headington Hill to Headington and ending at Headington Roundabout, where it meets the A40 and the Oxford Ring Road (A4142).

Large lorries are advised not to use the A420; congestion is common because some slow lorries still use it. The road has a poor safety record and was nicknamed the “A420 Road to Hell” in 2007. A 2018 survey called it the most dangerous A road in South East England.

History in brief: The A420 began in the early 1700s as a direct Chippenham–Bristol route via Tog Hill, bypassing Bath. Bath Road tolls started in 1707, and improvements occurred in the 1740s. In 1922 the A420 ran from Chippenham to Botley near Oxford; the Bristol–Chippenham section was then the A430, later renumbered as A420 when the two roads joined. The Botley–Headington part used to be part of the A40; after the northern Oxford bypass was built in the 1930s, that road became A420.

After the M4 opened in the 1970s, some sections were renumbered: Chippenham–Lyneham via Sutton Benger became B4069; Lyneham–Swindon became A3102; Swindon–Stratton St Margaret to the A419 became A4312.

Other notes: Rival matches between Oxford United and Swindon Town are sometimes called the A420 derby. Near Kingston Bagpuize, the A420 was the site of the fastest speeding offence caught in routine checks in the UK: in 2007 Timothy Brady was clocked at 172 mph and received a prison sentence.