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Route of the M3

Until very recently, the M3 was split into two sections, with the gap plugged by a few miles of the A33 at Winchester. The 1920s Winchester Bypass, one of the oldest pieces of dual carriageway in the country, and with intermediate junctions controlled by traffic lights, was left to deal with all the M3's through traffic.

In the way of the M3's completion was St Catherine's Hill — a very ancient and very important hill fort. This was all eventually thrown to the wind, and the Highways Agency filled in the gap at a cost of many millions of pounds and the slicing of a six lane motorway around the foot of St Catherine's Hill. It helped drivers just fine, but incensed environmentalists to the extent that large-scale road construction is barely possible today, and new roads dare not use the blackened word 'motorway'.

There are still people to this day who boycott the new part, between junctions 10 and 11, even though the old Winchester Bypass has been removed and grassed over.

At its southern end, the M3 is fortunate enough to have its traffic effectively distributed by the M27, which kindly prevents all six lanes from piling into the northern suburbs of Southampton.


Start London (A316)
Finish Southampton (M27)
Passes Staines, Bracknell, Basingstoke, Winchester
Length 61 miles
Connects to M25, M27, A34, A303

With thanks to Sam Borro, Ross Henderson, Johnny and James Denson for information in this section.