Second perhaps only to waterways, road systems have had the greatest impact on the design and physical structure of our cities. The car-centric redesign of the American city that began in the early 20th century was embraced with open arms by urban planners and citizens alike. Yet now, in the early 21st century, its limitations are clear. There is a rapidly growing awareness that simply expanding our roadways won't end congestion and gridlock.
The future, more and more urban transportation experts are coming to believe, lies in mobility-friendly networks in which cars are just one element -- and an ever-shrinking one as we move from a system in which the personally owned vehicle is king and toward a multimodal future of on-demand driverless vehicles, ride-sharing, expanded public transit, greater reliance on human-powered transportation and other alternatives.