What we learned from the Scandinavian countries--especially from Stockholm, Copenhagen, and the Netherlands--is that if you provide playgrounds, parks, and safe roads, it may take years, but everyone benefits from it. The children, the parents, and the seniors just get more into the streets. Nowadays in Copenhagen, most people walk and play outside, and just go to a café or whatever, but that wasn't the case 20 or 30 years ago. They took it a step at a time over a period of 30 or 40 years, but through environmental strategies, and that's the way they became more active.
On December 12th, 2011. See this statement in context.