I re-read chapter 1 in this book this morning Frank, Lawrence D. & Engelke, Peter O. & Schmid, Thomas L., Health and Community Design: the Impact of the Built Environment on Physical Activity (Washington: Island, 2003). The basic premise is that health determines how our cities are designed. The secondary and more important premise is that our sprawled cities were the result of healthy design against communicable diseases but have now been found to be lacking in providing environments in which to exercise and gain healthy physical activity. We have become dominated by the car design cities. Even 30 minutes of moderate exercise a day is an improvement to our health.