'Your grandchildren will snap across the entire continent in 24 hours on a new kind of highway and in a new kind of driverless car that is controlled by the push of a button," futurist Norman Bel Geddes promised in 1940. Mr. Bel Geddes designed Futurama, the most popular exhibit at the 1939 New York World's Fair, which in many ways inspired the construction of the Interstate Highway System.

Driverless cars have so far remained the stuff of science fiction. Seventy years after Mr. Bel Geddes's promise, they are finally close...