The A329(M) is a motorway in Berkshire, England. It is 4 miles (6.4 km) long and runs from the north of Bracknell to the south east of Reading. It is one of a small number of parts of the motorway system in England that are managed by the local transport authority, in this case Wokingham Borough Council, rather than Highways England.
From south to north, the route starts to the north of Bracknell and runs directly from the A329. It passes east of Wokingham in countryside. It then crosses the M4, continues north and meets the A3290 at Winnersh Triangle where it now ends. As originally built, the A329(M) continued to the junction with the A4, but this section has been since renamed the A3290. It is managed locally, Wokingham Borough Council, rather than by Highways England.
The first section of the road opened in 1973, and went from the Winnersh junction to a temporary terminus at the A321.
A further section to the North/West of Winnersh — due to open at the same time — took the road up to the junction with the A4 to the east of Reading, running to the north of the railway line and dividing the Earley area of Reading almost in two. However the opening of this section was delayed due to the collapse of the Loddon Viaduct on 24 October 1972, which killed three people and injured ten others. This section subsequently opened in 1974.
The third and final section to be completed was the southern section of the motorway which was built to a standard dual two lane motorway specification (D2), and was opened in 1975. This extended the road to the A329/B3408 junction at Amen Corner roundabout. The section of Berkshire Way (and the construction of the flyover) came some years later, allowing traffic to flow from Reading and the M4 past the official end of the motorway onto the Southern and Western industrial areas of Bracknell.
The large free-flow interchange between the A329(M) and the M4 was constructed as part of plans for an M31 motorway which was originally planned to extend down to the M3 (and possibly beyond) in the south.
In the early nineties the section of the A329(M) that met the A4 east of Reading was downgraded to an A road to enable the hard shoulder to be used by a park-and-ride bus service. It was then renamed the A3290. The Park and Ride bus service car park is subject to flooding and this causes frequent closures of the service.
A feature of the A329(M) is its wide grass central reservation north of the M4. The cross-section of the motorway was built in this way to support future widening to dual-three lane standard, which was never introduced: the later southern section to Amen Corner lacks this provision. Because of this wide central reservation, the A329 (M) was formerly one of the only motorways in the United Kingdom to have no central barriers on some stretches. However, as of 2010, almost the entire length of the road has had a central reservation barrier installed, possibly due to accidents over recent years.
In 2006, on an area to the south of the A329(M) just beyond the actual designated motorway section, construction began on a new housing development—Jennett's Park. A new roundabout retaining an eastbound through lane was built on the A329 to provide access to this development. It was finished in early 2011.
In 2015 the A329M was reduced to a single lane each way through Junction 10 by Highways England.