I’m a cyclist/pedestrian/motorist/transit-user. It just so happens that the most convenient, most cost-effective, and most enjoyable method for navigating my particular environment involves wielding a number of transportation tools. And I don’t think I’m very unusual in this respect.
The bicycle gets me to work or classes almost every day. Nothing beats it for speed and efficiency within certain parts of town. Walking is my mode of choice when I have extra time to soak in my surroundings, or I'm traveling a very short distance. The bus is useful every once in a while, especially in accessing less hospitable parts of Charlottesville like the U.S. 29 corridor. Finally, I share a car with my wife. Driving is convenient for grocery shopping in my opinion, and it is a requirement for traveling out of town. I use each of these modes almost every week.
I bring this up only to make the point that most users of the transportation system are probably as protean as I am. We have the flexibility to adjust as constraints and opportunities of our living environment change. The U.S census categorizes the modes commuters use into discrete “journey-to-work” units, and often policy analysis assumes that users are either motorists or not. Sharp categories mean change must be cataclysmic; blended categories mean change can happen through evolution.
Right now in most places around North America it would take some major transformations in infrastructure and land use to entice any given family to stop driving entirely. However, incremental improvements in infrastructure can lead to incremental changes in commuting. First, a once-a-week bike ride to work, then perhaps sharing one car between the family. The political will to make infrastructural changes and the transportation behavior of citizens are inextricably linked. If change happens in our transportation networks, it will have to ratchet between these two categories, one step at a time.