In the "Highways and Horizons" pavilion at the 1939-40 World's Fair in New York, General Motors presented Americans with "Futurama", a vision of the city of 1960. Norman Bel Geddes designed an enormous scale model, showing a utopian city rebuilt for the motor age, completely separating cars and pedestrians. Five million people came to see the exhibit, waiting more than an hour for their turn to get a sixteen-minute glimpse at the motorways of the world of tomorrow. There is a technicolor movie of the show online, as well as the accompanying book that Geddes wrote to explain his (and the motor industry's) ideas (or propaganda): "Magic Motorways".
Update: another movie here (via). Related: London traffic improvements (the Bressey Report, 1938).