Driverless cars are set to trigger gridlock chaos as they allow motorists to dodge massive parking fees, according to new research.
The controversial vehicles will be cruising slowly around cities with no one on board – saving their owners a fortune but clogging up the streets.
What’s more, low speed uses less petrol – so they will slow to a crawl to ‘kill time’, warns a leading transportation planner.
Chancellor Philip Hammond expects “fully driverless cars”, with no safety attendant on board, to be in use in just two years – by 2021.
The UK is the most expensive country in the world in which to park.
In London, drivers spend over £2,000 a year on charges – a third of the total cost of vehicle ownership.
Adam Millard-Ball, an associate professor of environmental studies at the University of California, Santa Cruz, said: “Parking prices are what get people out of their cars and on to public transit.
“But autonomous vehicles have no need to park at all.
“They can get around paying for parking by cruising.
“They will have every incentive to create havoc.”
The study published in the journal Transport Policy says the nightmare of “robot-fuelled gridlock” is right around the corner.
Prof Millard-Ball says self driving, or autonomous, vehicles are likely to become commonplace in the next five to 20 years.
So he carried out the first analysis of its kind into the combined impact of parking costs and the vehicles on city centres where the expense and availability of space is all that restricts car travel.
It found, under the ‘best-case scenario,’ the presence of as few as 2,000 self-driving cars in downtown San Francisco will slow traffic to less than two miles per hour.
Prof Millard-Ball used game theory and a traffic micro-simulation model to generate his predictions.
He likened it to the congestion caused at airports by motorists cruising the “arrivals” area to avoid paying for parking.
Prof Millard-Ball said: “It just takes a minority to gum things up. Drivers would go as slowly as possibly so they wouldn’t have to drive around again.”
Free smartphone parking areas, coupled with strict enforcement in loading areas, relieved the airport snarls.
But cities will be hard-pressed to provide remote parking areas for driverless cars at rates lower than the cost of cruising.
Prof Millard-Ball estimates this at just 50 cents an hour – about 30p in English money.
He said: “Even when you factor in electricity, depreciation, wear and tear, and maintenance, cruising costs about 50 cents an hour – that’s cheaper than parking even in a small town.
“Unless it is free or cheaper than cruising, why would anyone use a remote lot?”
Prof Millard-Ball said legislation also falls short because “it is difficult to regulate intent.”
He added: “You can pass a law saying it’s illegal to drive more than 10 minutes without a passenger, but what if the car is picking up a parcel?”
In his view the solution lies in “congestion pricing” which can take different forms but essentially amounts to a user fee.
In London’s city centre, motorists pay a flat fee of £11.50 (about $15) to enter. Singapore and Stockholm employ similar models.
More sophisticated systems could charge by miles driven, or assign different fees to particular streets.
Economists and environmentalists agree it effectively reduces congestion and pollution. But it is a politically fraught strategy because it raises the anger of commuters.
Prof Millard-Ball said: “As a policy, congestion pricing is difficult to implement.
“The public never wants to pay for something they have historically gotten for free.
“But no one owns an autonomous vehicle now, so there is no constituency organised to oppose charging for the use of public streets.
“This is the time to establish the principle and use it to avoid the nightmarish scenario of total gridlock.”
Moreover, driverless cars could be fitted with devices that would give policy makers options for levying fees based on location, speed, time of day – and even which lane they occupy.
Prof Millard-Ball said: “The fees could raise money for cities to improve transportation.
“The idea is to do it now before autonomous vehicles become widespread.”
He said the principle is straightforward, adding: “Self driving cars need to pay for using city streets – otherwise chaos will ensue.
“We need to discourage self driving cars from using city streets as a free parking lot.”
Last year a study found in London drivers are paying an average £2,239 on parking every year – and this does not include over spending on parking machines.
This overspend, for example buying two hours when you only stay for 30 minutes, is costing an additional £1,595.
The research found that on a per mile basis, UK drivers are spending 35 per cent more on driving than the US and Germany.
Prof Millard-Ball said: “Why would a self driving car pay $35 a day to park in a place like downtown San Francisco when cruising around costs less than 50 cents an hour?
“They just want to kill time in the cheapest way possible.”
By Ben Gelblum and Mark Waghorn