You could be forgiven for thinking urban traffic is already pretty bad. But it’s set to get worse, if the self-driving cars of the future spend their time driving around city centres to avoid paying parking fees.
That’s the view of transportation planner Adam Millard-Ball, an associate professor of environmental studies at the University of California, Santa Cruz, who believes autonomous vehicles will have every incentive to ‘create havoc’ on the streets.
“Autonomous vehicles have no need to park at all.”
“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,” says Millard-Ball. “They can get around paying for parking by cruising.”
His analysis, ‘The Autonomous Vehicle Parking Problem’, appears in the latest issue of Transport Policy. Millard-Ball believes the situation could be made worse by self-driving vehicles slowing to a crawl to save money by cruising at lower speeds.
At present, says Millard-Ball, the cost and availability of parking is the only tool that effectively restricts car travel in city centres. But as autonomous vehicles become commonplace, he warns, the impact of parking charges is set to change.
Using game theory and a traffic micro-simulation model to generate his predictions, his research found that in a best-case scenario, the presence of just 2,000 self-driving cars in downtown San Francisco could slow traffic to less than two miles per hour.
“It just takes a minority to gum things up,” he says, pointing to the congestion caused at airports when motorists cruised the ‘arrivals’ area to avoid paying for parking.
While the airports were able to provide free parking areas and strict enforcement, says Millard-Bell, cities will struggle to provide cost-effective parking areas for self-driving vehicles at a comparable cost – he estimates 50 cents per hour – to that of cruising.
“No one owns an autonomous vehicle now, so there's no constituency organized to oppose charging for the use of public streets.”
He believes the solution lies in congestion pricing – essentially a user fee to enter the city centre – similar to schemes in place in London, Singapore and Stockholm.
While such pricing can be politically difficult to implement, notes Millard-Bell, there is an opportunity to do so before autonomous vehicles are on the streets.
“As a policy, congestion pricing is difficult to implement. The public never wants to pay for something they've historically gotten for free,” he says.
“But no one owns an autonomous vehicle now, so there's no constituency organized 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.”