An opinion piece in the WSJ on July 17 criticized investment in the proposed bullet train between Los Angeles and San Francisco. It then advocated preparing the road infrastructure for the advent of driverless cars: The number of lanes should be increased because driverless cars can cope with narrower lanes. Trucks should be limited to one or two wider lanes (ideally separate from car lanes). Traffic flow control systems would have to be installed to optimize traffic flow – both on the highway and in the city where stop lights often increase congestion.
The author points out interesting issues but fails to recognize the decentralized nature of the driverless revolution. These cars do not require modifications to the existing infrastructure. They will drive where a human can drive. But their behavior and economics differ. They will naturally improve the flow of traffic. Driverless cars increase the peak capacity of the existing infrastructure because they can safely keep shorter distances to other cars. Even a small percentage of driverless cars mixed into regular traffic can reduce congestion by adopting an optimal speed or by simply keeping side-by-side with another (automated?) car in two-lane pile-ups effectively preventing other cars from lane-hopping. The cost-structure of driverless car sharing and the need for demand management by mobility providers are also important factors that will reduce peak loads on the traffic infrastructure.
There is no need for driverless road infrastructure investment. Governments would be well advised, however, to invest directly into advancing driverless technology. Fewer traffic accidents would save hundreds of millions of dollars every year. Better road utilization exhibited by driverless cars will also greatly lower the costs for building and maintaining the road infrastructure.