Autocar’s trips to the Paris auto show are always marked by one, unchanging, characteristic: spectacular traffic congestion.

The trip from our hotel last week (close to the Arc de Triomphe) to the exhibition centre at Porte de Versailles, a distance of no more than five miles, took over an hour in the morning rush hour.

The return journey to the Gard du Nord railway station was even worse. The 10-mile journey, around the vast, six-lane, Périphérique urban motorway took nearly 90 minutes.

Only some tidy rule bending by our German driver managed to get us out of total gridlock and within walking distance of Eurostar.

On paper, Paris’s chronic congestion doesn’t make sense. The city benefits from a huge number of wide, spacious boulevards as well as a proper urban motorway. The tube system is extensive and, thanks to the amount of road space in the city, a new tram network has been built.

However, after a few hours in the jams, I reckon I know how Paris could free its roads. Introduce the Boîte Jaune.

If you look closely at this snap from the Mercedes Viano, there’s a large panel van stuck in the middle of our carriageway. Once this happens at most of the junctions in a small area, gridlock is guaranteed. The irony is that roads just a few hundred yards away can be completely empty.

The easy way out of this problem is to install that most plus l'anglais of solutions, the yellow box. While the average French driver might not be minded to obey any traffic rules, I have no doubt that they would suddenly find themselves much more able to enjoy the capital’s superb roads.

The glorious anarchy of the Arc de Triomphe roundabout, where drivers on it give way to drivers coming onto it, seems to work amazingly well, however.