Prepare For Gridlock If Future For Autonomous Vehicles Is Plentiful Cheap Journeys

Hiring a taxi is expensive. This is mostly because of the cost of the human driver. Replacing that driver with a robot will clearly reduce the cost. That is the one of the key promises of autonomous vehicles (AVs)—in the future, we will be able to travel where we want, when we want at low cost because we will no longer own cars and nor will we have to pay the high costs of human drivers.

It is a fundamental principle of economics that when the price of a good decreases, the quantity demanded increases. In other words, make something cheap, and people will buy lots of it.

Make motoring even cheaper than it is today, and people will consume even more of it. In that scenario, the future for AVs is gridlock.

If, instead, the cost of using or hiring driverless cars is high, they will be mostly used by those who can easily afford them, much as the hiring of taxis today is mainly the preserve of the rich.

The supposed spatial benefits of replacing human drivers with computer ones—such as platooning and cars’ ability to drive bumper to bumper—are unachievable if driverless cars mix with human-driven vehicles.

Despite the possible pitfalls ahead, many politicians continue to lobby for AVs. Writing on ConservativeHome.com, Southampton Councillor Tom Bell said on February 15 that the U.K. should “rapidly adopt clean personal transportation” because it would improve the “safety, cost and convenience” of urban travel.

He urged local councils to embrace an AV future because driverless cars “will free up council time for more productive pursuits and free up urban land for development.”

Bell, a cybersecurity consultant, added that “smaller cities, towns and rural communities stand to gain the most from AVs.”

Councils should start providing infrastructure for AVs and, in the meantime, should stop providing infrastructure for cyclists, Bell argued.

“In an attempt to reduce emissions, many local authorities, including the Labour-run Council in Southampton where I serve, have been excessively replacing valuable space on roads with under-used cycle lanes,” he wrote.

When pressed, he told me he cycles.

“I’m a cyclist, I cycle regularly around the city, and it infuriates me the way that Southampton’s drivers drive. But I’m also a technologist, and I can’t see any reason why, as a cyclist and a pedestrian, I won’t find myself more settled, more at peace, more in harmony with car users, as AVs are rolled out.”

If the roll-out of AVs leads to more traffic congestion—a prediction Bell disputed—the solution, he said, was to build more roads.

“As you roll out technology that’s beneficial to people, people are attracted to it. And we should encourage them to be attracted to good things. If congestion continues to increase, there is scope to improve the capacity of roads: it won’t require the whole country being [covered in asphalt]; it will just require a steady, moderate response to growing demand. Building extra roads in order to ease congestion [will] enable more people to have access to convenient transport.”

On the contrary, there’s much evidence that building more roads does not reduce congestion; it increases it.

Induced demand

Whenever a new road is built, or an older one is widened, a greater number of people decide to drive more. Transport wonks know this as “induced demand.”

Urbanists have a pithy phrase to describe this phenomenon: “Building more roads to prevent congestion is like a fat man loosening his belt to prevent obesity.”

This quote was paraphrased from a 1955 article by Lewis Mumford. Writing in The New Yorker, the great urban planning specialist suggested that “[experts believe congestion] can be solved by increasing the capacity of the existing traffic routes ... Like the tailor’s remedy for obesity—letting out the seams of the trousers and loosening the belt—this does nothing to curb the greedy appetite that [has] caused the fat to accumulate.⁠”

Mumford was describing the as-yet-unnamed concept of induced demand in transport. This theory was described in detail in 1969 by J.J. Leeming, a British road-traffic engineer and county surveyor. He observed that the more roads are built, the more traffic there is to fill those roads.

Leeming’s idea was conceived shortly after German mathematician Dietrich Braess released his paradox which demonstrated that “selfish” motorists could not be relied upon to consider the optimal travel times for all rather than just themselves, leading to delays for all.

If you remove “selfish” motorists and replace them with cooperative computers, much of the unused space between moving motor vehicles could be reclaimed. However, it’s likely such savings would be consumed by an increase in journeys.

To replicate the way people might use AVs, researchers in 2018 gave subjects in San Francisco free chauffeur-driven vehicles for a week. The provision resulted in increases in vehicle-miles traveled and an overall increase in the number of trips. Many of the trips had no rider in the car as the subjects sent the chauffeur away, no parking was required.

Lead author Mustapha Harb, of the University of California at Berkeley, surmised that access to AVs would not only encourage people to take cars for trips they would not have bothered with before but could also lead to the rise of what he called “ghost trips” where people send an empty car to pick up their shopping or fast-food order.

According to research by Adam Millard-Ball, an associate professor of environmental studies at the University of California, Santa Cruz, the use of AVs could lead to a doubling of vehicle travel within cities.

Agreeing that the “advent of autonomous vehicles will revolutionize transportation” Millard-Ball said that his 2019 study predicted that the advent would also lead to “unambiguously negative environmental consequences,” including traffic congestion.

This congestion would be caused by fleets of driverless cars cruising the streets without the need to park.

“AVs can behave strategically in order to minimize the costs to their passengers or fleet owners, primarily through seeking out and creating their own traffic congestion through choosing to circle on streets where they can drive the most slowly,” concluded Millard-Ball.

Static parking lots would no longer be needed but, instead, the parking lots would be mobile, with AVs coordinating automatically to lower their costs by choosing the same set of streets to circle.

“The agreed-upon set of streets would, in effect, be transformed into a mobile and very slow-moving parking lot,” said Millard-Ball.

Tech bros to the rescue

If AVs chose to drive to a parking lot away from the urban core to save on fees, this would “increase vehicle miles traveled because of additional travel to remote lots,” warned a 2016 study from the RAND Corporation.

Such downsides will be overcome, believes Cllr Bell.

“Increasing the accessibility and availability of fast, cheap, convenient, low-cost transport for everyone, including the poorest in our society, not just those that can afford taxis, is something that we should want and celebrate,” he told me in a telephone interview.

“It would be foolish for us to seek to suppress or delay or frustrate the process of technological improvement simply because there are some problems.”

Technology will come to the rescue, he said: “Our society is structured to identify problems and generate solutions.”

Sidestepping the fact we’ve had more than 100 years of motorized traffic congestion that hasn’t been reduced by building more roads, he added: “If there are increases in the overall volumes of traffic on our roads that’s something that can be overcome; it can be overcome through increasing the capacity of roads; it can be overcome through self-driving capability, like platooning, where cars can bunch up closer to each other.”

A more likely result of AV take-up will be the decimation of public transit, suggested a report by the World Economic Forum and Boston Consulting Group.

“Congestion will increase [with use of AVs],” said the 2019 report, “because commuters will likely choose the new vehicles over public transportation.”

AVs could prove to be “cheaper than existing public transport, even if the latter is subsidized,” predicted the report.

And, as was shown above, making something cheaper leads to more of it being consumed. Cheap AV travel won’t free the streets of cars; it would clog them.