As for flying cars, we’ll likely see isolated use over the next decade, but we won’t see widespread use until after autonomous non-flying cars are a mainstay.

Virtually every automotive manufacturer has now got on board with the idea that autonomous vehicles are the future, and that future is fast approaching. The exact form that this paradigm shift will take is anyone’s guess, and billions of dollars have been spent by companies looking to ensure that they are at the forefront of this sweeping change.

Two new forms of transportation that have long been consigned to science fiction are finally looking to become reality and the race is on to capture the new market. Where some companies are putting their money behind subterranean travel, others see flying cars being sold in car dealerships as the future of transport.

The promise of a better future

Roads can only widen so much before being unwieldy and encroaching on buildings. Adding new roads, highways, overpasses, bypasses, and other increasingly huge infrastructure does little to solve the problems of gridlock. Adding new or better roads simply means more cars are bought to fill them and the problem of traffic quickly returns.

Going underground

Companies like Elon Musk’s The Boring Company and Richard Branson’s Virgin have thrown their weight behind huge underground tunnels as a potential solution for this problem. Autonomous vehicles riding at high speeds could transfer a large number of people a great distance quickly, reducing the number of cars on the surface.

It’s an idea that people can quickly understand, even if the scale of the feat is daunting. A future with cities sitting atop 30 stacked tunnels serving road traffic, a Metrorail system, and a high-speed Hyperloop transit system capable of reaching up to 760 mph.

Tunnels, once built, are out of sight, weatherproof, and safe. Those living on the surface should be virtually unaware and undisturbed by the vast infrastructure underneath, both when it is being built and when it is being operated.

Whereas traditional train tracks and roads take up huge amounts of real estate and divide communities, underground tunnels run under the surface.

The Earth’s crust is conveniently thick, so in reality, there are few practical limits to the number of tunnels that could be built upon each other.

Compared to a future with flying cars, subterranean travel has fewer actors and would appear to have fewer legislative and ethical considerations to worry about. People are also used to the idea of traveling underground in their own vehicles or on trains.

Boring huge tunnels under cities is, however, extremely expensive. Much of the recent work on underground systems has been on research attempting to reduce the cost of digging these large tunnels. Reducing the diameter of the tunnel, increasing the speed and power of boring machines, lowering tunneling downtime, automating some of the boring steps, and switching diesel engines to electric motors are some of the ways they hope to reduce costs and make these large-scale projects more feasible.

Then there is all of the existing under-city infrastructure that you have to worry about — water pipes, subways, power lines, gas lines — not to mention the structural foundations of skyscrapers that often reach deep into bedrock.

Is the answer in the skies?

Those behind autonomous air travel reason that flying cars solve the three-dimensional challenge that normal automotive travel faces. Flying cars are not constrained by the physical size of the road and they offer a whole new verticality, hugely increasing the number of vehicles that could be operating in the same area at the same time.

Spokespersons from Intel have advised they expect to see flights with autonomous flying cars before 2025. Though these would initially be rare, they say, within 10 years we can expect to see larger fleets of air taxis from companies like Uber. In fact, Uber is on record saying they hope to launch air taxis in around four years, with commuter aircraft being tested as early as 2020. Dealership lots may quickly fill up with land-based used cars if all goes to plan.

But there are still significant hurdles for flying cars to overcome. Public perception of flying cars will need to improve significantly before the system would work at scale, particularly where it comes to safety. Though autonomous vehicles, to date, have had an excellent safety record, it takes a leap of faith to entrust your life to an automated flying vehicle. Weather can be harsh and unpredictable; how will your automated flying car capable of a maximum airspeed of 80 mph handle wind speeds of 90 mph?

Critics also cite the potential dangers to pedestrians and third parties that a large number of flying cars could create. There may need to be central bodies in charge of ensuring autonomous flying vehicles are maintained to a high standard.

Then there are considerations such as where can flying cars land, and how are all of the competing autonomous flying vehicle companies’ cars going to communicate and negotiate with each other regarding things such as airspace and landing queues.

It’s also true that flying vehicles are noisy. Anyone living near an airport will tell you that it’s no joke, so one must consider the potential noise pollution of thousands or even millions of flying cars everywhere you go.

The software in autonomous flying vehicles will need to be highly secure. The first news stories of terrorists hacking into such a system could kill the idea before it got off the ground (no pun intended).

Where flying cars look to be the solution to one problem, they introduce a number of new, complex issues that are only partially addressed right now.

Conclusion

We are probably likely to see a complex combination of both solutions and others being used around the world.

In locations where long, straight, underground tunnels could connect large cities, they potentially make a lot of sense. In the Middle East, China, and India, conditions are ideal. In the Middle East, with an underground tunnel you could get from point A to B very quickly while avoiding a desert. In India, a Hyperloop underground track could cut the three-hour train journey from Mumbai to Pune to 25 minutes. Feasibility studies continue, and research into better boring technology should result in lower costs.

As for flying cars, we’ll likely see isolated use over the next decade, but we won’t see widespread use until after autonomous non-flying cars are a mainstay.