the m27 is a motorway in hampshire, england. it is long and runs between cadnam and portsmouth. it was opened in stages between 1975 and 1983. it is unfinished, as an extension to the east was planned. a number of smaller motorways were proposed, connecting the city centres of southampton and portsmouth to the motorway; of these only the m271 and m275 were built. three sections of the m27 have since been widened to four lanes each way, the first between junctions 7 and 8, the second between junctions 3 and 4, and the third begins at the slip road where junction 11 joins until mid-way to junction 12.