It takes a long time. Vancouver, BC was very successful with this because they built a new transit system back in the '80s (Skytrain) and then clustered density around the stations. It's been extremely succesful, and there is also a complimentary system of bicycles boulevards for people to ride bikes.

Here in the US, however, the car rules, for better (but mostly) worse. I had an incident on my bike last Monday in Palo Alto with a car where I fell and broke my hand.

Trying to code with a broken hand is rather... interesting.