In 1935 Sir Charles Bressey was appointed by Hore-Belisha, Minister of Transport, to make a comprehensive and systematic survey of the roads of Greater London. It was clear that the infrastructure required radical improvement to keep up with the expansion of traffic and Belisha said that Bressey's report "would stir the imagination of the whole country".
The report was published three years later and laid out a reconstruction scheme for London based on a detailed 30-year plan for highway development. Bressey's plan to deal with traffic involved tunnels, overhead roads, new arterial and circular highways and 'parkways' linking the city to the rest of the country. Before any of this could be implemented the plan was interrupted by war and aerial bombardment. Nevertheless, many of Bressey's ideas would influence post-war reconstruction and subsequent schemes for the capital's reorganisation.
Source (if you're in a UK school or library, you can access a movie about it).
Via Ptak Science Books, where you can see more illustrations of the "traffic improvements" outlined in the "Bressey Report". Check out this blog, by the way, there is much more to be found (about 900 posts on the history of ideas and technology, to be precise...). It is written and illustrated by John Ptak, an antiquarian science bookseller.
Related: Magic Motorways, a similar plan for US cities.
"Roadtown", Edgar Chambless, 1910.
The Deutsche Fotothek has uploaded a mind-blowing portfolio of around 3,500 drawings and documents by German visionary Karl Hans Janke. Via BibliOdyssey, where you can find a selection and an introduction in English about the man and his work.
"As the earth’s population steadily increases, so does the pressure to open new frontiers. While the oceans have long been used for transportation, this book is an extended thought experiment about how they could support permanent settlements. Considering these issues will be invaluable no matter which way humanity next expands. In particular, the ocean bears some definite similarities to space: the final frontier, which will surely be an important part of our near future."
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).