Cars that drive themselves seemed like science fiction just a few years ago, but recent demonstration projects have shown that the technology is already here. Self-driving car technology, pioneered by Google, has advanced so quickly that its ubiquitous presence on city streets is now simply a matter of time. Boosters say that mass-market autonomous cars are only three to five years away; others estimate at least 10 years. No one doubts they are coming.

But ideas about how these cars will affect cities and the environment seem to be stuck in the past. People think of self-driving, or driverless, technology as something added on to personal cars. Personal cars, however, spend 95 percent of their time parked, going nowhere, and waiting until they are needed. It’s more likely that city dwellers will view this technology as a service, like calling for a taxi. In principle, an on-demand car service could offer the door-to-door mobility of car travel without the fixed costs and hassles of owning a car.

Self-driving technology could cause a societal shift away from private car ownership and toward vehicle sharing. Widespread use of on-demand car services would result in fewer vehicles, which would then transform urban land use. Cities could reap significant benefits: fewer parking lots, more relatively dense, walkable neighborhoods, cleaner air, and reduced carbon emissions.

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Car2go cars.

Matt BiddulphCar2go cars.

Car-sharing programs like car2go offer spontaneous, one-way, pay-by-the-minute rentals within a prescribed service area. Members use a smartphone app to locate a nearby car, get to it, swipe a card to unlock, and drive to their destination. When they get there, users park the car at the curb and walk away, leaving it available for the next user.

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Now imagine a mash-up of this popular model and Google’s self-driving car technology. The car-sharing fleet could be retrofitted with self-driving navigation systems. (Let’s call the hypothetical startup company “Car2Google.” Of course, other car-sharing services like Zipcar or even traditional rental car companies could jump into the game.) Layering self-driving technology onto this system would allow people to order a car from a fleet and have the car pick them up. It’s a taxi service without the drivers. Users would summon a car with their phone and wait comfortably indoors. The car would call or text them as it approaches. Users would then hop in, talk on the phone, or nap while the car drives to their destination. Once there, they can just walk away. The service charges their credit card an amount based on the time or length of the trip.

In addition to improving car-sharing for the 1.7 million people who already use such a service, driverless technology would expand the appeal to a wide range of people, including those who:

  • are too young to drive;
  • are too old or infirm to drive;
  • have had their license suspended;
  • are too drunk or stoned to drive safely.

Parents could safely deliver their children to or from soccer practice or play dates simply by ordering a vehicle for them. Elderly people who should no longer be behind the wheel and disabled people who cannot drive would still have mobility, with the travel arrangements made independently or by caregivers. And everyone would benefit from impaired late-night revelers having a safe way to get home.

Does this sound like a fantasy? Rapid changes just in the last year bring this idea a lot closer to reality.

  • Driverless technology is becoming more reliable, safer, and cheaper. Google’s six autonomous vehicles being tested in California have already logged more than 300,000 miles without incident. A Romanian teenager and an Israeli company have created low-cost versions of a self-driving car.
  • Car-sharing is an established program ready for technological breakthroughs. The popular car2go already serves 18 cities in North America and Europe. It is adding more cities all the time.

Self-driving vehicles would vastly increase the efficiency of car-sharing. When not being used, cars would drive toward potential users instead of sitting idle and waiting for users to come to them. Instead of having workers going out into the field to service the fleet, cars could go to a central location when on-board sensors or user feedback recommend maintenance. A vehicle would take itself offline, drive itself to be washed or have its oil changed, and then put itself back online when ready to pick up another customer.

Driverless technology would also allow for a greener fleet. Urban trips are usually short hops ideally suited to electric vehicles. And when the battery level drops below a certain threshold, an autonomous vehicle could go offline and drive itself to the nearest available inductive charging pad to recharge.

Many households are already giving up their second vehicle — or sometimes even their only one — in favor of a mix of car-sharing, bicycling, and using mass transit. A convenient, self-driving shared vehicle service could accelerate this trend. Traditional vehicles would likely still be needed for camping trips or to pick up a load of gravel, for instance, but these specialty vehicles could also be rented, perhaps from the same company.

This scenario of a city buzzing with fleets of self-driving vehicles may sound futuristic, but existing technology can already do everything described here. Automated car technology can also be applied gradually, one element at a time. Commercial airliners and many transit systems are already nearly fully automated.

The legal system and insurance interests are predictably wary of self-driving cars, and it will take time for individuals to grow comfortable with the idea of taking their hands off the wheel and their feet off the pedal. But legalization has already begun in several states, the internet is rife with remarkable self-driving car videos, surveys show popular acceptance of the idea, and Google’s test models have a spotless safety record thus far.

A Google rendering of what a self-driving car "sees."

A Google rendering of what a self-driving car “sees.”

Although the future is murky and the impacts of this system are unclear, if such a service took off, cities could enjoy a wide array of benefits.

Less traffic: Studies have shown that each car-sharing vehicle takes between nine and 13 privately owned vehicles off the road. When people pay for driving by the trip, they see the real costs; therefore, car-sharing members drive 44 percent less than personal vehicle owners do. Cruising to find parking spots would no longer be an issue, thereby eliminating a third of traffic in some urban areas.

Fewer parking spaces: More than a third of land area in some U.S. cities is dedicated to car storage. If people shift away from personal cars and toward shared vehicles, most of those parking spaces would become unnecessary. Acres of empty parking lots and driveways in desirable locations would open up for more productive uses like housing, playgrounds, or parks. If the change happens quickly, urban land prices could tumble.

Safer streets: People are terrible drivers. Human error causes or contributes to more than 90 percent of car crashes. Getting behind the wheel is the riskiest thing most people do in a day. Self-driving cars would be programmed to never speed, make sudden lane changes, or let drunk or distracted drivers make life-or-death decisions. The lead engineer on Google’s project expects driverless cars to sharply reduce crashes of all kinds.

Cost savings: Personal car ownership costs about $9,000 per year. Among young people especially, rates of driving and car ownership are already falling. A convenient car-sharing service that saves money could convince people to sell their cars while allowing them to maintain their same level of mobility.

Environmental benefits: More efficient travel patterns, fewer vehicles, cleaner cars, and less driving overall would lead to better urban air quality and lower carbon emissions. Less land would be paved over for parking, reducing stormwater runoff and heat island effects. These sustainability benefits would be market-driven and would not require government subsidy.

As with any potentially disruptive technology, the benefits might not materialize in the way we predict, and the future might not be as rosy as it seems. Consider the techno-pessimistic future:

More traffic: Economists are quick to point out that people usually consume more of something when it becomes cheaper. If people can sleep or work on their laptops while in a car, perhaps they will drive more and commute even longer distances. We simply don’t know how much unmet, latent demand there is for vehicle travel. In addition, trips that previously did not exist would result from new users (children, blind people), people who shift from mass transit, and the self-redistribution of empty vehicles driving to the next user.

Sprawl: Currently, only a small number of workers are super commuters who live an hour or more by car from their jobs. But if technology can eliminate the fatigue and aggravation of driving, more people may choose this lifestyle. The boom of streetcar suburbs in the 1890s and, later, auto-oriented suburbs in the 1940s showed that new modes of transportation have big effects on where people choose to live.

Less safe streets: If fewer cars sit parked and more of them are constantly circulating, streets could become busier. Early testing has been very promising, but self-driving cars have not been set loose on the full range of chaotic real-world conditions such as erratic drivers, snow-covered streets, and software or mechanical glitches.

Job losses: Certain workers lose out in this imagined future. Cab drivers, parking lot attendants, transit workers (who will likely be displaced not only by driverless cars but also driverless buses and trains), car dealers, and repair shops will become less necessary. Other jobs might pop up to replace them, but it is uncertain what they would be.

Widespread adoption of self-driving cars might just be another techno fantasy that won’t ever come into being. After all, vehicles powered by fuel cells (or hydrogen) or jet packs never came to pass. But autonomous cars are different because they can arrive incrementally. Cars already have cruise control, anti-lock brakes, lane sensors, and parallel parking assist. Soon private cars will be able to operate autonomously but only on highways and only when you choose to turn it on, then on city streets, and then eventually as Car2Google. Early adopters could be freight companies, then city buses, and then courier services. Unlike other technologies, it can function without everyone using it or a massive new fueling infrastructure in place. Self-driving technology can be layered onto existing cars using existing streets.

The public policy response to self-driving cars depends on how likely they will come into widespread use and how soon. Taking the pessimistic view, if this will never be more than a niche phenomenon, we should let the geeks play with their toys and ignore them. Driverless technology might find use in long-haul trucks or trains, but it won’t change cities in any significant way.

But what if we are only a decade away from being able to cheaply add self-driving navigation to any vehicle and on-demand automated car services suddenly take off? If that happens, today’s cars-first development policies will have been catastrophically wasteful. For example, if fleets of self-driving vehicles take hold, ubiquitous local laws that require each building to have its own oversupply of free parking will have wasted billions of dollars and vast acreages of urban land. Just so, in a future with fewer vehicles traveling through the system more efficiently, committing ourselves to multibillion-dollar roadway expansions is an enormous mistake. Buildings, parking garages, and highways are 100-year decisions. There is a built-in inefficiency with mass motoring, where every adult owns an expensive, space-consuming piece of capital equipment that sits idle 95 percent of the time. Our grandchildren may look back on this era as a short-term aberration, solved by technology.

The timing of self-driving cars and their possible impacts are uncertain. Nevertheless, the future leans toward transportation as a shared service. For decades we didn’t have the technology to allow one car to quickly and easily serve the needs of many people. Despite the inefficiencies of everyone owning his or her own vehicle, rules and cultural biases made the idea of car-sharing seem not only impractical but even contrary to human nature. But we now have the technology; Zipcar and car2go have proven the market; investors see opportunity; and change is coming very quickly.

Naysayers have questioned the viability of car-sharing since 1998, when there were only four car-sharing vehicles in our hometown of Portland. Today, there are more than 1,100 here, with a few more added every week. Car-sharing hasn’t stalled or died; in fact, it has exploded in popularity. Adding self-driving technology into the mix could make the next phase of car-sharing truly transformative for both users and cities.