Doctor Evil wrote:

Because Chicago is built on a grid system, not a medieval street pattern.
The business section in the morning is light in traffic, as only traffic
going there is actually there. None running straight through as happens in
the west end of London. Before the congestion charge, surveys found that
the majority of vehicles in the west end were just passing through. It is
those that need to be discouraged.

The grid system has little to do with the ability to park your car in
downtown Chicago to take the family to the museums. What Chicago has is
planning for the use of cars by the population and willingness to change
the road layouts on a grand scale where necessary. As the morning rush
hour lasts about 4 hours, your comments on light traffic are a joke!
London has failed miserably on new routes, because of the obsession with
the existing public service Underground. The Chicago through traffic is
predominantly N/S and is on both the toll roads, which are cheap enough
for the customers to be prepared to use them and the central zone.
London doesn't even have one decent through route!!

Regards
Capitol