Driverless vehicles would be a windfall for households and businesses that acquire them but would probably increase traffic and nationwide fuel usage.
Google and other innovators are working on vehicles that someday might drive themselves with little or no attention from human passengers. The vehicles of the future will have fast, observant computers that automatically communicate position and road conditions with other vehicles on the road.
Driverless vehicles are expected to help children, the blind, the elderly and others who currently cannot safely drive themselves. Helped by their huge amounts of data and computing power, driverless cars are also purported to reduce traffic congestion and nationwide fuel consumption by driving smarter.
But smarter driving will lead to more driving, because smarter driving reduces the cost per mile of vehicle usage. The end result of additional driving could be more traffic and more aggregate fuel consumption.
These days, a driver has three main costs of the trip to consider: fuel consumption, vehicle wear and tear, and time and attention devoted to driving that could be for something else. (Drivers also need to consider other costs of vehicle ownership, such as the purchase price and the cost of insuring the vehicle.)
Fuel and wear and tear cost roughly 50 cents a mile, which is why employers reimburse employees for job-related personal vehicle usage at about that rate. At an average speed of 30 miles an hour (including stops, traffic conditions and so on), each mile takes two minutes of driver time. For those who value their time at more than $15 an hour, the time cost of the trip exceeds the combined fuel and wear and tear costs.
Research has shown that cutting travel costs through reduced gas prices causes people to drive more, for example by eschewing carpools and public transportation. A driverless car should also cause people to use their vehicles for more miles, because they could use their time in the car to sleep, work, watch television, read a book and do other things they might normally do at home.
Households and business may also begin to use vehicles with no human passengers or drivers in order to move goods from one place to another and, by economizing on the human driver costs, they may want to move more goods than they do today.
As people take on additional activities in their personal vehicles, they may also demand larger vehicles that necessarily require more fuel per mile.
Before driverless cars are adopted, a number of hurdles must be cleared. Some refinements in vehicle technology need to be resolved; insurance companies and state regulators must also figure out liability issues.
Even if driverless vehicles led to more congestion and more aggregate fuel consumption, driverless vehicles would be a welcome technological advance, because the billions of hours that people already devote to driving could be put to alternative uses.
But expect new driving technologies to increase the number of vehicles on the road.