A404(M) motorway

A404(M)
The northern end of the A404(M)
Route information
Length:	2.4 mi (3.9 km)
Existed:	1961 – present
Major junctions
From:	Holyport
	M4 motorway A308(M) motorway
To:	Woolley Green
Location
Primary destinations:	Maidenhead, (High Wycombe), (Henley)
Road network
Roads in the United Kingdom Motorways A and B road zones

The A404(M) is a motorway in Berkshire, England and can be referred to as the Maidenhead West Bypass. It joins the M4 with the A404 dual carriageway to High Wycombe, Marlow and the M40. It was once known as the A423(M).

The A404(M) leaves the M4 at Junction 8/9, and heads north, passing Maidenhead and forming 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 Marlow before joining the M40 at the Handy Cross roundabout outside High Wycombe.

The road was originally opened in 1961 as part of the A4(M) Maidenhead Bypass 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 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. When the M4 was extended in 1971, 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. The old M4 was renumbered A423(M) as it was a direct continuation of the A423 to Oxford.