A404
A404 Harrow Road, at junction with Chippenham Road on the left
Route information
Length	44.6 mi (71.8 km)
Major junctions
From	A40 (Westway) inMarylebone,London
Major intersections	A219 A406 A312 A410 A412 A413 A416 A355 A40 A308 A4 M25[1] M40[2] M4
To	A404(M) atMaidenhead
Location
Country	United Kingdom
Primary destinations	Wembley,Harrow,Northwood,Rickmansworth,Amersham,High Wycombe,Marlow
Road network
Roads in the United Kingdom Motorways A and B road zones
←A403 →A405

TheA404 is a road in the United Kingdom that starts atPaddington inLondon and terminates nearMaidenhead inBerkshire. It is 44.6 miles (71.8 km) long.

The road initially follows a course through north-west London viaHarlesden,Wembley,Harrow,Northwood andRickmansworth. During this stage, it is known asHarrow Road. It crosses theM25 at Junction 18 atChorleywood, crossing intoBuckinghamshire and then continues towardsLittle Chalfont andAmersham.

Between Harrow and Amersham, the road closely follows the route of the London – Harrow-on-the-Hill – Aylesbury railway lines,London to Aylesbury line fromMarylebone, and runs near several stations along that line.

At Amersham Common, the road turns south-west and continues in that direction joining the Amersham by-pass (A413) for a short distance, and then proceeds towardsHigh Wycombe. After passing through the town centre, and crossing theA40, it changes to a dual carriageway up the hill to theM40 Junction 4, and continues as a dual carriageway pastMarlow andBisham.

The road eventually becomes theA404(M) atMaidenhead Thicket. It then runs a short distance towards theM4 where the A404(M) finally terminates at Junction 8/9.^[3]

TheHarrow Road is an ancient route^[4] inNorth West London which runs fromPaddington in a northwesterly direction towardsHarrow. It is also the name given to the immediate surrounding area ofQueens Park andKensal Green, straddling the NW10, W10, W2 and W9 postcodes. With minor deviations in the 19th and 20th centuries, the route remains otherwise unaltered.

Harrow Road is also a ward of the City of Westminster. The population of this ward at the 2011 Census was 12,034.^[5]

By the 19th century, Harrow Road had become the main street inPaddington.^[6]

In the 20th century, many properties along Harrow Road were developed into high-rise social housing, though some 19th-century houses and commercial buildings north of thePaddington Basin were retained. These includedElgin Towers, constructed between 1966 and 1969, and demolished in 1994.^[6]

The 1950 filmThe Blue Lamp is set around Harrow Road and features it prominently.^[6]

In one version of theBus Driver's Prayer, the line fromThe Lord's Prayer, "Hallowed be thy name" is replaced with "Harrow Road be thy name."^[7]

A404(M)
A404(M) highlighted in blue
The northern end of the A404(M)
Route information
Maintained byNational Highways
Length	2.4 mi (3.9 km)
Existed	1961–present
Major junctions
Northeast end	Maidenhead (west)
Major intersections	M4 motorway[8] A308(M) motorway[9] J9b ->A4 road
Southwest end	M4 Junction 8/9
Location
Country	United Kingdom
Primary destinations	Maidenhead, (High Wycombe), (Henley), (Marlow)
Road network
Roads in the United Kingdom Motorways A and B road zones
←A329(M) →A627(M)

TheA404(M) is amotorway inBerkshire, England and can be referred to as theMaidenhead 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 theA423 between Maidenhead andOxford was reclassified as theA4130.

The road was originally opened in 1961,^[10] as part of the A4(M) Maidenhead Bypass,^{[citation needed]} which ran from the existing Junction 7, through a junction with theA308 and ending at a junction with theA4. In 1963, theSlough bypass was opened to Junction 7,^[10] 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 ofReading, instead of north of it.^{[citation needed]} When the M4 was extended in 1971,^[10] 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, theA308(M), was built to maintain access to the A308 and connected with the A404(M) and the M4 at the samegrade separatedroundabout. This new junction was numbered 8/9 so as not to confuse motorists and the interchange with the A4 became Junction 9A.^{[citation needed]} The old M4 was renumbered A423(M)^{[citation needed]} as it was a direct continuation of the A423 toOxford.

This article contains a bulleted list or table of intersections whichshould be presented in a properly formatted junction table. Please consultthis guideline for information on how to create one. Pleaseimprove this article if you can.(December 2021)

Information above gathered from Advanced Direction Signs April 2011

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