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.