Beginning in the 1920s, American urban growth was planned to encourage residents to leave congested city centres and move to the peripheries or to newly created suburbs. There, homes, schools, shopping and the office were all too far away to walk or cycle.
The article is interesting, but the above quote is a little off, I believe. The highway system in America was designed because the dept of defense needed a good way to move troops around the country in the event of an invasion. The suburbs sprang up as a side-effect of the highway system because people did not want to live in urban centers anymore. It became easier for them to commute by car using the interstates.