Even though driverless cars have only been popular in the news for a few years, it's looking increasingly likely that they're the future of personal vehicle travel. Already, California and Nevada have taken steps to approve the use of Google's model, and Google co-founder Sergey Brin believes autonomous vehicles will be commercially available within a decade. The advantages to driverless cars are numerous and significant, but they raise serious questions about how we invest in infrastructure as the technology matures. In particular, are we wasting billions on highway capacity that will soon be obsolete?
There's a lot to like about autonomous vehicles. There's great potential for them to be operated much more safely than manually-driven vehicles, and if this bears out it'd be justification enough to make the switch. They would also reduce the need for parking directly adjacent to destinations, since the car could drop you off and find a space further afield. It'd also be easier to save a lot of money by getting rid of your own vehicle, instead taking advantage of a massive fleet of cheap, robotic vehicles.
Then there's congestion.
According to a recent study by Columbia University's Patcharinee Tientrakool, a highway populated exclusively with driverless, communicating vehicles could increase its efficiency by up to 273%. In this scenario almost four times as many cars could travel through a corridor, safely and quickly, as are currently able to do so. This is mainly thanks to the decreased following distances required by autonomous vehicles--about 100 feet at 60 mph for humans, compared to less than 20 feet for computer-driven vehicles--and their ability to coordinate speeds, merging, etc. Although not absolutely equivalent, fully adopting driverless cars would be akin to more than tripling the number of lanes of every highway in the country.
Whether that transition takes twenty years or fifty, it's coming. (And if it doesn't, it will be because of some other revolutionary technology that solves the problem even more effectively.) Given that reality, and with vehicle miles per capita on the decline, continuing to invest scant transportation dollars on increased capacity is a monumentally wasteful practice. According to a Congressional Budget Office report [PDF], we spent about "$146 billion to build, operate, and maintain highways in the United States," about two-thirds of that paid for by state and local governments, in 2007 alone. Not all of this is capacity expansion, but you can count on the fact that a great deal of it is. This is at the same time as the American Society of Civil Engineers is telling us that we've got a $2.2 trillion infrastructure backlog, and the longer we wait to make these necessary repairs the more expensive they'll become.
In urban areas it costs tens, sometimes even hundreds of millions of dollars per mile to add new highway lanes--and in as little as a generation we're going to be forced to to tear them right back out.
It's been said again and again, but it really is time to turn the corner and start investing more in the maintenance and repair of our ailing transportation system, and directing funds toward projects that do more for promoting health, sustainability, and economic productivity. It's understandable, if not acceptable, that the threat of increasing population and traffic congestion has made it difficult to focus on simply maintaining what we already have. It's increasingly clear, however, that this is no longer a question of useful expansion vs. useful repair. Only one choice makes sense for our future. We can do better, and we're running out of excuses for failing to do so.