When advocates of self-driving cars discuss their potential benefits, reducing traffic congestion usually shows up near the top of the list.

Whether these autonomous vehicles, as planners call them, will significantly reduce congestion, however, may depend on who owns them — individuals, as with the vast majority of today's cars, or a transit system, or a different social ownership network.

Congestion issues could also depend on how well AVs can be integrated with public transit and things like ride-sharing and ride-hailing technologies like Uber and Lyft.

For starters, a private AV can let you off at your destination, then go somewhere else to park. That alone would reduce congestion in downtowns, considering that, today, up to a third of drivers in urban centres are looking for parking.

Today's privately-owned cars are parked an average of 95 per cent of the time. Tomorrow's AVs that are not privately owned could let you off and then go on to let off another passenger, or pick up a new passenger nearby.

Michele Bertoncello, an AVs expert with the international consulting firm McKinsey and Company, estimates that AVs could reduce needed parking space in the U.S. by more than 5.7 billion square metres, an area about the size of Prince Edward Island.

Of course, a crunch comes during rush hour, when demand will likely exceed supply, and that may be a reason why time-sensitive people will want their own.

Ownership models

Michele Bertoncello, with consultancy firm McKinsey and Company, speaks in Florence, Italy in 2014 about his research on autonomous vehicles. (McKinsey & Co.)

As for ownership, informed opinions vary. Bertoncello expects private ownership will be the dominant model, like with today's cars.

On the other hand, Don Tapscott, the Toronto-based digital technology expert, anticipates driverless car networks operating mostly under some form of social ownership, possibly with a pay-per-use model like music streaming.

Many AVs could be part of the public transit system, while others could be owned and managed by what Tapscott calls a socially-owned enterprise, using the same technology as the cryptocurrency Bitcoin, the block chain.

Noah Goodall, a research scientist studying AVs for the Virginia Centre for Transportation Innovation and Research, expects both models will be around for a while.

"Single ownership makes a lot of sense in rural areas and for certain people," he says, while shared-ownership or a subscription-based model — perhaps like driverless taxis — could appeal to more people in more densely populated areas.

Todd Litman, executive director of the Victoria Transport Policy Institute, speaks at a workshop for transport planners in Istanbul, Turkey in June. (IETT)

In fact, for people who cannot drive because of a visual impairment or any other issue that affects their mobility, AVs could become quite popular.

Goodall expects many of today's two-car families will end up owning one AV while relying on shared vehicles for the rest of their transportation needs.

Todd Litman, with the Victoria Transport Policy Institute think tank, estimates it will be "cost-effective for a family to give up one of their cars if they're driving it less than 10,000 kilometres a year." Which means even once AVs dominate the roads, many families will still have good reasons to own a car.

Last mile challenge

For traffic congested cities, integrating AVs with public transit may offer hope.

Imagine if AVs can service what urban planners call the last mile challenge — getting people home from a train or subway station a few kilometres away.

A mix of AVs from single passenger to minibus-size vehicles providing door-to-door service could help get many commuters out of their own cars and onto transit.

Goodall points to the work Google is doing on low-speed electric AVs, which can go up to 40 km/hr. These are vehicles that could integrate with public transit and "really help" with that last-mile challenge, he says, imagining lightweight vehicles AVs linking up together and creating a virtual bus or road train.

The new Google pod car isn't designed for a long trip, or a joyride. It lacks air bags and other federally required safety features, so it can't go more than 40 kilometres (25 miles) per hour. (Tony Avelar/Associated Press)

In the interim, before the AV era, connected cars that will communicate with each other electronically through wifi so they can move in sync and more compactly on expressways, could help reduce traffic congestion.

Bertoncello feels that a big advantage of AVs is the potential to give over a billion drivers 50 extra minutes of free time per day, which could also have huge economic impact.

Still, Litman cautions that, while these vehicles may indeed reduce traffic, congestion and emissions, he also says that their advocates are often seeing them through rose-coloured glasses.

For example, if AVs are publicly owned, he says, there's the challenge of keeping the interiors clean and not smelling something like an old subway station elevator.

Both Litman and Goodall also suggest that the widespread use of AVs could lead to additional vehicle traffic because they will increase travel convenience and affordability. Some people may even want an AV that serves as a mobile office or a bedroom.

Safety and road infrastructure

​There's nothing like a crash to slow down traffic, and the general view is that once AVs account for the vast majority of vehicles, accidents, and the deaths and injuries that result, should go way down.

Mounted on a swivelling motorized arm, the steering wheel on a Rinspeed Budii self-driving electric city car can be used to drive from either side of the car, and rests in the middle of the dashboard when not in use. (Reuters)

But during the mixed transition, both Litman and Goodall say there is no guarantee of improved safety. Goodall also wants to see a long testing period for AVs first.

Bertoncello points out that assisted driving technology in the cars of today is already improving safety. And the sensors on AVs will provide "the kind of data that is the dream of every car engineer today," resulting in safety problems getting detected much sooner and hopefully solved.

He also doesn't foresee much change in road infrastructure during the transition period, even if it last decades, because "it would just be too costly."

As he sees it, "full autonomous and manual driving must be able to co-exist, as lots of people will want to have the option to manually drive their AV."

AVs a paradigm shift?

In a February report on AVs, Litman wrote that the AV "is certainly not a 'paradigm shift' since it does not fundamentally change how we define transport problems."

Don Tapscott, whose books include 'The Digital Economy' and 'Paradigm Shift,' says the AV should cause a paradigm shift because it breaks our mental model about two separate kinds of transportation, private and public. (The Leigh Bureau)

But Tapscott, who wrote the book Paradigm Shift, one of 15 he has authored or co-authored, expects that will indeed be the outcome.

"A paradigm is a mental model, and paradigms put boundaries around what we think and constrain our actions, and they're based on assumptions that are so strong that we don't know that they're there."

Our current paradigm around transportation, he says, is that there are two models, private and public, the latter limited to government ownership, not the social ownership he foresees.

"It's precisely a paradigm shift because it's breaking our mental models of what is transportation, but, because of technology, it's now possible to have a whole new model that combines both public and private at much lower cost and with significant benefit to the population."

This story is the second of a two-part series. The future of traffic looks at how commuting apps and technology might impact urban traffic in the years before the AV era.