Leslie Hook:

When the muddy streets of San Francisco were laid out during the heady days of the gold rush, riding a horse was the fastest way to get around. Today a new type of vehicle can be seen cruising the city: the driverless car.

With their spinning radar sensors and bulky camera arrays, these vehicles have the awkward look of a technology that is not quite mature. Yet just as the automobile gave rise to paved streets and suburban sprawl, the driverless car is set to radically reshape the cities we live in.

“There are huge changes that are coming,” says Dan Doctoroff, former deputy mayor for economic development and rebuilding in New York. “We are in the middle of a historic moment.” Today Doctoroff leads Sidewalk Labs, a one-year-old offshoot of Google that works to bring new technologies to cities.