A version of road pricing already exists in central London in the form of the £15-per-day congestion charge and the ultra-low emission zone charges introduced under Mayor of London Sadiq Khan. 

Meanwhile, the “full-fat” version of pay-per-mile, where Uber-style dynamic pricing changes on a daily basis, is possible but would be even more complex to manage. 

Under that model, however, Marlow at the Adam Smith Institute argues that the Government could get the best possible picture of how busy roads are. In one potential scenario, the UK could adopt French-style privatisation of motorways, with companies then using the system to judge where to invest in upgrades or new carriageways.

“If we can work out how much it costs to drive on the road, we can therefore signal about where investment is needed,” Marlow says. 

“Let’s say you’re in central London and the cost to drive on a stretch of road is very high. That signals to the Government or to private investors that they’ll get a great return for investing in that road.”

Another alternative is for city-specific congestion charges, like the one already in place in London, to be coupled with a per-mile system, both the Campaign for Better Transport and the Resolution Foundation have argued.

Risking a backlash

While economists may love road pricing, the general public are unsurprisingly more sceptical.

Some 55pc of motorists remain opposed to any form of pay-per-mile taxation, a poll by the Green Insurer found in May, with just 17pc saying they were in favour.

Against that backdrop, Steve Gooding, a former senior Department for Transport official, believes road pricing advocates face major pitfalls. 

Gooding, now director of the RAC Foundation, still has the scars from the last time Labour proposed the controversial idea.

In 2007, he and other officials watched as thousands of people per day joined the e-petition in protest over plans they had put forward with then-transport secretary Alistair Darling.

“Our experience was that if you try to protect your income stream and get the policy benefits of road pricing – for example tackling congestion – you have immediately made your scheme more complicated,” says Gooding.

“So if you’re going to introduce a new scheme that will affect millions of people, you want to look for the simplest, most foolproof, most bulletproof way of going about it.”

Fears about the potentially astronomical fees motorists could end up paying under the previously proposed system – not helped by its lack of simplicity – were also what led to it being junked by ministers ahead of the 2010 election. 

“One challenge with a system where people pay different amounts of money at different times and in different places is that inherently someone, somewhere is going to be paying more and somebody else is going to be paying less,” Gooding adds. 

“And we all know that the person most likely to want to talk to [the media] is the person who ends up paying more.”

Critics also point to concerns about how pay-per-mile systems, particularly those that charge more based on the type of road or time of day, can punish people who may need to drive to work because they cannot afford public transport – or aren’t served well by it. 

This could include many people living in rural areas, where bus services have been reduced over the past decade, or key workers such as nurses, social care workers and police officers who may need to work early and late shifts.