Highways will handle three times as many cars

the PopMechanics Brain Trust : scientist
According to researchers at Columbia University, vehicles driven by humans use at best 5 percent of a highway's road surface at any given time. If we let technology take the wheel, we could significantly increase the volume of traffic. In one example, Volvo's semiautonomous road train wirelessly connects a stream of cars to a truck driven by a professional. The self-driving cars mimic the speed and steering of the lead vehicle, safely decreasing the gaps while increasing fuel efficiency

Popular mechanics, (2012) "110 Predictions For the Next 110 Years", [online], Available: http://www.popularmechanics.com/technology/engineering/news/110-predictions-for-the-next-110-years