Cynics might ask what could be mysterious about an orbital motorway, and what could be interesting about a road in Belgium? Well, if you drive on it regularly, you can't but help scratching your head at its idiosyncrasies – so here at least are the curiosities of the Brussels ring road.

Like many products of the Belgian planning system, it is a structure that evolved, rather than was rigorously planned. Or rather there was a plan, but it was then scrupulously ignored. This step-by-step approach can have its charm, but also its scary moments – ask any Bruxellois about the old style Carrefour Leonard¹, if you want to see them go pale for a moment. Up until 2008, it was the number one accident black spot in Belgium. Essentially, two very busy motorways would meet each other without the benefit of a proper intersection – you had to turn across oncoming traffic in order to go from Paris to Brussels or some other road less travelled by; it was literally taking your life in your hands. Since 2008, some turn-offs have been blocked, fortunately – if you want to go east coming from Brussels, you now have to go west to the next junction and then turn round there.

The first mystery is the most prosaic –  why doesn't it go all the way round? Currently, if you want to go from Ghent to southeast Brussels, you have to go north, three quarters of the way round the clock, or even worse, deviate miles south via Waterloo². The Belgian equivalent of the AA would like to fill in this gap, but as it will only bring even more traffic to an already gridlocked road, there is not much urgency.

In any case Brussels residents have long memories of how their city was devastated by uncontrolled concrete. They know very well that the original plan for Brussels was to turn it into a Belgian equivalent of Spaghetti Junction, with half a million people somehow wedged into the gaps. What's more, as with nearly everything in Belgium, there is a strong 'Communautaire' angle – Brussels residents suspect that some Flemish people see Brussels principally as a handy place to join up the motorways coming from Ghent, Antwerp and Leuven, all the better to never need to visit Brussels itself. In addition, the bit where the gap is (Uccle), in the southwest of the capital, has residents with deep pockets, and strong pressure groups.

The actual reason for the gap goes back to the 1970s. The ring road was built in stages, as and when money became available. By the time they'd got to the most tricky bits, through one of the richest suburbs and one of its outstanding natural features – the Soignes forest – public and municipal pressure was such that it was just shelved. The oil crisis had in any case demonstrated that the car as a universal transport model had had its day. Every now and then, people dust off 'improvements' to the ring. One example is a recent Flemish idea to make everything on their side twice as wide – in reality, however, it seems unlikely. Even more unlikely is the latest innovation to fill the 'gap' – an enormous tunnel under the forest – as this would cost an arm and a leg. This bit-by-bit approach explains some smaller mysteries – why for example, there is a wine shop and what looks like private houses right beside one section. Nice if you like car spotting. This bit, to be fair, is not officially a motorway – still chock full of cars though.

However, there is another, greater mystery. Picture the scene – you are driving from the airport, east of Brussels, and you want to go towards Paris. All is normal as you speed through the lovely Soignes forest³, past the turn-off for Waterloo, Lasne and other places where the rich burghers of Brussels have built their villas, and then all of a sudden – surprise – all the traffic going to Paris, Brussels, Mons and other such places, is squeezed off onto a slip road and three broad lanes lead on to what the innocent visitor must assume to be a very mighty metropolis, Ittre.

Except it isn't. Ittre has an overcrowded prison – the subject of several prison officer strikes in recent years, a village/small town with a bit of history, some pleasant countryside walks and that is it. It's another vestige of some long-forgotten road building project, where presumably the three lane motorway to a village would have flowed onwards to some more notable destination. One can only imagine how many tourists have been down these few kilometres, convinced they are still on the motorway for Paris, only to be sorely disappointed. There are lots more of these leftovers if you care to look for them – what investigative journalist Jean-Claude Défossé called 'Great Useless Works'. A whole interchange in the commune of Forest was built and then abandoned – the resulting freed up land creating a bit of a shopping centre.

Aside from these little mysteries, there are some elements of "The Ring" that are wearily predictable. With seven million journeys over it every day, and a lot of those being commuter traffic, it is jammed solid every morning, every evening and every time there is an accident. Until Brussels does something like the congestion charge in London, that is how it is likely to stay.