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COMPUTING SCIENCE

Leave the Driving to It

How would lives and landscapes change if every car had a computer in the driver’s seat?

Brian Hayes

Paving Paradise

One aspect of car culture that would have been hard to foresee in 1911 is the extraordinary importance of parking. Although estimates vary, it seems there are two or three parking spaces for every car in the United States; think of it as one space at home, one at work, and a share of one at the mall. At just two spaces per car, this works out to 500 million spaces in all, covering a total area of at least 3,000 square miles. A suburban shopping mall dedicates more land area to parking than to retail space. In dense central cities, parking spaces become a crucial limiting resource; they are the throttle valve that determines how many cars can come downtown. A study by Donald Shoup and his colleagues at the University of California, Los Angeles, shows that 30 percent of the drivers in some business districts are driving in circles, searching for a parking place.

The solution suggested by the cybercar fantasy is automated valet parking: The car drops you off at the front door, then drives away to find a parking place on its own. When you’re ready to leave, you call for the car and it comes to fetch you. In this scheme, the parking facility need not be within walking distance of your destination, so it can be moved out of the central business district. Likewise the suburban mall no longer has to be an island in a vast sea of asphalt. Another advantage of having cars park themselves is that they can squeeze together more tightly. (For one thing, there’s no need to leave room for opening doors.)

All these strategies for making car trips more convenient and less tedious have to be seen as an inducement to ever-greater reliance on private vehicles. People will tolerate longer commutes if they can read or nap while in transit. They’ll take the car to the city if they don’t have to worry about where to park it. Thus a likely result of automotive automation is further diffusion of population over the landscape.

Another seemingly inevitable effect of more private vehicles is less public transit. However, all the advantages of computer-driven vehicles are also available to transit operators. Indeed, it’s even possible that the distinction between public and private vehicles would blur a little. In a world where cars drive themselves and come to you when beckoned, there’s not a lot of difference between calling for your own car and calling for a shared vehicle. For that matter, in a world where cars drive themselves and know their way around, there’s not a lot of difference between a taxi and a rental car. Short-term rental programs such as Zipcar might thrive in this environment.

The effects that driverless technology would have on energy consumption and carbon-dioxide emissions are hard to gauge. Given the same basic engine and vehicle, replacing a human driver with a computer ought to improve fuel economy. Platoons of closely spaced cars traveling together also save fuel through aerodynamic efficiency, although the effect may be small except at NASCAR speed. More important is the ability of cooperative scheduling and traffic management to avoid needless braking and acceleration. All of these factors are encouraging, but if the technology leads to more trips and longer trips, gains could turn to losses. And then there’s the issue of all those empty ghost cars shuttling back and forth to remote parking lots or running errands on behalf of their owners. The average occupancy of vehicles on the road could fall below one person.





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