M31 motorway

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M31
Route information
Length	22.0 mi (35.4 km)
Status	Unbuilt
History	Never built; partially completed as A329(M) and A3290
Major junctions
southeast end	M25 motorway
Major intersections	M3 motorway M4 motorway
northwest end	M4
Location
Country	United Kingdom
Primary destinations	Bracknell Wokingham Reading
Road network
Roads in the United Kingdom Motorways A and B road zones

The M31 was planned as a Reading to M3 motorway which was dubbed the 'M3 – M4 link motorway'. It would have provided a direct high-speed route between the two motorways. The motorway was planned at the same time as the largely unrealised London Ringways scheme and an additional section was planned that would have taken the M31 south and east from the M3 to connect to the scheme's Ringway 4 (now the M25) providing a shorter route for traffic travelling between the west and Surrey and Kent.

Only part of the planned route was built; it bears the designations A329(M) and A3290. Had the motorway been constructed it would have provided an alternative to the south-west section of the M25, reducing the motorway journey between Reading and Byfleet by approximately 10 miles (16 km) and alleviating traffic on what is the M25's busiest section.^{[1][failed verification][2]}

• Pathetic Motorways
  • M31
  • M31 route map
  • Map of planned northern section of M31/A329(M)
• CBRD – A329(M)

51°24′58″N 0°48′15″W / 51.41602°N 0.80423°W / 51.41602; -0.80423