The ‘Autoflow Road’ will link Tokyo with Osaka through underground tunnels, along hard shoulders and central reservations, never needing to stop for rest, food or lavatory breaks.

The Japanese government will present a detailed plan for the project this summer.

Although the precise route has not yet been worked out, the relatively small containers, holding up to one tonne of goods, will travel alongside existing roads, as well as through purpose-built tunnels, operating unmanned around the clock and delivering as much in a day as 25,000 human drivers.

By taking freight off the roads, the idea goes, the project will reduce congestion and pollution on surface roads and railways and leave them freer for the use of non-commercial travel.

“As we anticipate a decreasing population … the Autoflow Road is very important,” Japan’s transport minister, Tetsuo Saito, said last week. “It responds not just to the distribution crisis, but reduces greenhouse gas emissions, improving the convenience of the society as a whole, including passenger transport, and increasing productivity.”

It is a reaction to what is being called the “2024 problem”, a confluence of circumstances that is threatening to paralyse Japan’s logistics.

As the country’s population shrinks, so does its workforce: the number of delivery drivers is expected to drop from 660,000 in 2020 to 480,000 in 2030. That will be less than two thirds of the number needed to handle a projected 1.4 billion tonnes of freight.

Meanwhile, new labour rules introduced last year limit overtime for lorry drivers. Worst hit will be remoter regions such as Tohoku in the northeast, which was stricken by the 2011 earthquake, and the southwestern island of Shikoku.

No precise schedule has been set so far but the hope is that the first of several stages of the network will open within ten years. Japan is not the only country planning such a cargo conveyor belt, but if it fulfils its ambitions it will have one of the biggest.

Japan has not published a detailed estimate but the Yomiuri Shimbun newspaper estimated it at 80 billion yen (£400 million) per 6-mile stretch.