The A404(M) is a motorway in Berkshire, England and can be referred to as the Maidenhead and Marlow Bypass or M4/M40 link road. It joins the M4 with the A404 dual carriageway to High Wycombe, Marlow and the M40. It was originally known as the A423(M) until the A423 between Maidenhead and Oxford was reclassified as the A4130.


The A404(M) leaves the M4 at Junction 8/9, and heads north, passing through the western suburbs of Maidenhead, forming part of the town's western bypass before terminating at a junction with the A4 just outside Maidenhead. The road becomes the A404 which continues north passing north west Maidenhead and Marlow before joining the M40 Junction 4 at the Handy Cross roundabout at High Wycombe.


The road was originally opened in 1961[1] as part of the A4(M) Maidenhead Bypass[2] which ran from the existing Junction 7, through a junction with the A308 and ending at a junction with the A4. In 1963 the Slough bypass was opened[1] to Junction 7 and the A4(M) was renumbered M4, Junction 8 being with the A308 and Junction 9 with the A4.

The proposed route of the M4 was then changed to go south of Reading, instead of north of it.[3] When the M4 was extended in 1971,[1] a new junction was provided to connect with what would become a spur. As this new interchange was built too close to the existing Junction 8, this had to be closed. A new spur, the A308(M), was built to maintain access to the A308 and connected with the A404(M) and the M4 at the same grade separated roundabout. This new junction was numbered 8/9 so as not to confuse motorists and the interchange with the A4 became Junction 9A.[4] The old M4 was renumbered A423(M)[5] as it was a direct continuation of the A423 to Oxford.

Over time the A423 was superseded by the M40 and the A404 was improved to dual carriageway standard, with a new routing. Since the road now ran through a rebuilt junction 9B onto the A404, this motorway spur was reclassified A404(M) in the 1990s


A404(M) motorway
Northbound exits Junction Southbound exits
Road continues as A404 to Marlow and Wycombe
Oxford (M40) and Henley (A4130)
Reading, Maidenhead A4
Reading, Slough, Windsor (M4) A404(M)
Reading, Maidenhead A4 Start of motorway
Cox Green, White Waltham J9A Cox Green, White Waltham
Start of motorway

High Wycombe, Henley, Maidenhead (West) A404(M)
M4 J8/9
Maidenhead A308(M)
South Wales, Reading M4(W)
London, Windsor, Slough M4(E)

Information above gathered from Advanced Direction Signs April 2011

See also


External links

Route map: Google

KML is from Wikidata