M3 motorway (Great Britain)

M3
M3 highlighted in blue Show interactive map Shown with UK motorway network Show UK motorways map
Looking south at Twyford Down
Route information
Part of E05
Maintained by National Highways
Length	59 mi (95 km)
Existed	1971–present
History	Opened: 1971 Completed: 1995
Major junctions
Northeast end	Sunbury-on-Thames 51°25′00″N 0°25′26″W / 51.4166°N 0.4240°W / 51.4166; -0.4240 (M3 motorway (northeastern end))
Major intersections	J2 → M25 motorway J14 → M27 motorway
Southwest end	Chilworth 50°57′16″N 1°24′29″W / 50.9545°N 1.4081°W / 50.9545; -1.4081 (M3 motorway (southwestern end))
Location
Country	United Kingdom
Counties	Surrey, Hampshire
Primary destinations	London Bracknell Aldershot Basingstoke Winchester Southampton Reading Newbury
Road network
Roads in the United Kingdom Motorways A and B road zones
← M2 → M4

The M3 is a motorway in England, from Sunbury-on-Thames, Surrey, to Eastleigh, Hampshire; a distance of approximately 59 miles (95 km). The route includes the Aldershot Urban Area, Basingstoke, Winchester, and Southampton.

It was constructed as a dual three-lane motorway except for its two-lane section between junction 8 (A303) and junction 9. The motorway was opened in phases, ranging from Lightwater/Bagshot to Popham in 1971 to Winchester to Otterbourne Hill in 1995. The latter stages attracted opposition from environmental campaigns across Britain due to its large cutting through wooded Twyford Down; numerous road protests were held which delayed its opening. Similar protests were avoided on the near-parallel A3 by the construction of the Hindhead Tunnel. Since completion, the motorway has been an artery to the west and midsections of the South Coast and Isle of Wight including for tourism. The major settlements nearest to the motorway are served by a railway also used for commuting but are relatively dispersed. Traffic on the M3 sees delays and congestion on its busiest sections near commuting hotspots and during holiday periods. From Chertsey to Fleet the road was in 2017 converted to a Smart Motorway, turning the hard shoulder into a permanent fourth lane with emergency refuge lay-bys.^[1]