It is forty years since cars first rolled onto the M27 motorway. 

The 25 mile long motorway runs between Cadnam on the edge of the New Forest, skirts the top of Southampton and eventually reaches Portsmouth in the East. It is fed by the M3 which brings traffic from the M25 and the rest of the UK road network.

It is undoubtedly a significant birthday, but there is a suggestion that it is not actually finished.

The birthday is only really relevant to the first part of the motorway which opened in August 1975 between junctions one and two. It was open as far as junction four by December 1975 with the whole length being finally accesible by 1983.

Folklore suggests that the original plan for the M27 was for some sort of south coast superhighway, linking to the major trunk roads in the west and stretching all the way to the channel ports at Dover, giving a clear run from the west country to the continent. The Pathetic Motorways website, which is a brilliant resource for time wasting road trivia, says this was never really the case.

Such a proposal was mentioned by the Institution of Highway Engineers in 1936, but it was never aired beyond that. One reason would be the viability of such an expensive road building project, but also the difficulty of bulldozing a path through both the New Forest and Dartmoor National Parks would be sensitive, both politically and environmentally.

In fact the original plan for the motorway was for it to reach Chichester and become a motorway to run along a significant length of the UK's south coast. The research from Pathetic Motorways says that plans were very much afoot for the M27 to continue beyond the current end in Portsmouth, with extra spurs and appendages.

Some were built, such as the M271 Totton Spur which squirts motorists into the western end of Southampton, and the M275 into the heart of Portsmouth. The proposed M272 into Southampton was never built as a motorway, but now exists as the A335.

Check a map and you'll see the M27 seems to stop just shy of the A3(M). However full motorway standards are in place until east of the A3M interchange and Highways England manages it as motorway as far as that, so it could be said that it is a motorway in all but name as far as there. 

Although road building is now back on the government agenda, it seems unlikely that the M27 will ever be significantly longer than it is currently so we can probably conclude that it is in fact, complete.

Whether or not a western extension would have been desirable probably depends on your point of view. If you live along the proposed route, you'll be glad the plans never got anywhere. If sat in long queues on the A303, A30 or M5 toward the west country on the August bank holiday however, it will seem like a missed opportunity.