Phil didn't want to hear about statistics, so I will answer his question instead, what is the solution?
I'll make it simple. The Plat of Zion. This was the city designed by Joseph Smith, the founder of the Mormon religion. It has won awards from the American Planning Association and it really has a lot of merit. The design is set into square miles. Each square mile will have a population of about 15-20 thousand people. When a city grows larger than that, a new city will be built next to it. The city is based around a city center consisting of schools, churches and government buildings. Commercial areas are also in the city center. All of the houses were located in the city so that everyone had the same access to health care, education and cultural events. The farmers would 'commute' to their farms. Each city was surrounded by agriculture where crops and animals were raised. It was a great design with lots of potential.
However, there were some problems. First off, the planning was pretty strict by current standards. At some point of 'planning' you start borderlining on socialism. That's not the direction we want to go. Additionally, while many cities have characteristics of the Plat of Zion design, few have stuck with it over the years. Sterling in Southern Alberta Canada is as close as it gets to a true living Plat of Zion. About 800 people live in Sterling and you could say that the city didn't really strive. Other cities in the area were designed after the Plat of Zion, but with growth eventually gave up the plan. So it is the failure of the city to strive that has made the Plat of Zion a success in one city.
What we need to do is rebuild the entire world using the plat of Zion design and all of our problems will be solved. Sorry, I suppose you wanted realistic solutions. The point of that discussion was that every city is designed differently and has their own unique problems. I live in a city that is well designed and I can walk most anywhere within the city. The problem is enforcement of laws. Motorists speed and don't stop at cross walks making it extremely difficult to navigate the city by foot. Additionally, traveling outside of the city is difficult because there are only two roads going North, one is a 4 lane highway with a 2 inch shoulder, the other is a bumpy back road that is experiencing increases in traffic volume. I am working to increase pedestrian and bike awareness with police and I'm working to maintain a through route to the north for bike traffic.
Each city will be different, the last city I was in had wonderful enforcement of laws protecting pedestrians, but the transit system was border lining on non-existent.
The solution is complete streets and mixed use zoning. Really the solution lies in your hands. You need to be at your city planner's office making sure that he knows that you need sidewalks and wide shoulders to get around town. He needs to know that you value a walkable community. He needs to know that you aren't 'anti-car', but pro-community and that will be aided by walkability. He needs to know that you are not the only person with your particular view. You also need to be present and vocal at planning commission meetings and city council meetings. Express your views and show that it is not only economical, but it will make the city a better place.
We need to be working with city planners to make zoning more advantageous for small businesses and more difficult for large box stores. We need the people of the community to vote with their money for the smaller businesses. We have to show the decision makers that we want smaller shops and walkable scale so that when they invest in small, there will be a return in investment greater than there would be for big box stores (that means paying more and shopping at your neighbor's store). We need to recognize the potential problems arising in our communities and bring them to the attention of the decision makers. We need to be educated on city government procedures and we need to be active in the process. Put simply, if we want to make a difference, we have to live what we preach and be involved.
While the solution varies greatly between cities, it all revolves around an involved community, walkability, complete streets and mixed use zoning. We have a lot of retrofitting to do, but there is a lot of room to make things better. I hope this post isn't too vague, it's hard to get down to 'the solution' when it's different in every city.