M3 Motorway (Great Britain) - Detailed Routing

Detailed Routing

The motorway starts as a dual three lane route at Sunbury on Thames on the edge of South West London. It heads south west, crosses the River Thames on the M3 Chertsey Bridge to the north of Chertsey and passes under the M25 motorway, before continuing in a more westerly direction south of Camberley. From Junction 4 it runs across the northern suburbs of Farnborough it enters a more rural setting, crosses the South Western Railway Main Line, and passes close to the Basingstoke Canal before reaching the outskirts of Basingstoke. Turning south west again, it runs across the south of Basingstoke, before reaching Junction 8, where lane 1 becomes the A303 road and the motorway continues as a dual two lane road through open countryside and Micheldever Wood until it reaches the north of Winchester.

Forming the Winchester Bypass it widens to three lanes at Junction 9, continues directly south and then into a small loop around the east of the City. It runs through a deep cutting in Twyford Down and then proceeds south west again, crossing the South Western Railway Main Line a second time alongside the River Itchen and back into a more urban environment before crossing the Eastleigh to Romsey railway line and ending at the Chilworth Roundabout on the fringes of Southampton.

A bridge known as the Spitfire Bridge carries the B3404 Alresford Road to Winchester over the M3 motorway, and the parallel A272 which is known as 'Spitfire Link'. It replaced a concrete parabolic arch bridge under which a Curtiss P-40 had been flown by George Rogers in October 1941. It was generally assumed locally that the aircraft had been a Spitfire and so the name 'Spitfire Bridge' stuck. It is still used for the replacement bridge.

A private exit off the northern roundabout at Junction 4a provides access to the UK headquarters of Sun Microsystems. The A325 has a roundabout junction with a minor road over the M3 between junctions 3 and 4, but there is no junction with the motorway.