Will self-driving cars cause ‘gridlock’ on city streets?

Self-driving cars could cause severe traffic problems by cruising around streets simply to avoid paying parking fees, a study has found.

A newly published research paper by Adam Millard-Ball, an associate professor of environmental studies at the University of California, Santa Cruz, says that it may be cheaper for autonomous vehicles to drive around while unoccupied rather than stopping.

As tech news site Digital Trends notes, unlike vehicles operated by humans, cars controlled by computers “can keep cruising around once its passenger has disembarked”. Drivers can then simply summon the car using a smartphone app.

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Using a combination of game theory - the study of how decision making can influence others - and complex traffic simulation models, Millard-Ball determined that it would take just 2,000 autonomous cars to slow traffic to an average of “less than two miles per hour” in San Francisco, says MIT Technology Review magazine.

Millard-Ball said that while hefty parking fees “are what get people out of their cars and onto public transit”, autonomous vehicles “will have every incentive to create havoc” unless preventative measures are taken.

“Even when you factor in electricity, depreciation, wear and tear, and maintenance, cruising costs about 50 cents [38p] an hour – that’s cheaper than parking even in a small town,” he added.

What can be done?

Millard-Ball suggests that cities may have to implement further congestion charges in a bid to persuade autonomous vehicle owners to park their cars when they reach their destination.

Such levies could include “a time-based charge for occupying public highways”, whether a vehicle is parked or in motion, or a fee for the amount of distance covered while the car is unoccupied, Auto Express reports.

Since the technology is in its infancy, “no one owns an autonomous vehicle now, so there’s no constituency organised to oppose charging for the use of public streets”, adds Millard-Ball.

He concludes: “This is the time to establish the principle and use it to avoid the nightmarish scenario of total gridlock.”