Transportation systems, as we know them today, will simply not sustain the worlds’ growing population. Imagine a projected population of nine billion individuals. If this future population had mobility patterns like drivers in the United States, there would be a staggering 7.6 billion motor vehicles, using 440 million barrels of oil and producing 62 billion tons of CO2 per year. John Sterman says it is self-evident that our current transportation model simply will not scale. But, since the gross world product (GWP) is growing at 3.2% annually, and doubles every twenty years, our current model of development is an overture for environmental disaster.  It is clear to Sterman that we need to think differently about the problem. People need access to goods, services, people, and opportunities. This access is what traditional forms of transportation provide. We also need to see transportation in its complexity, and expect that our planning efforts will have totally unintended, unexpected “rebound” effects. Sterman provides two examples of these rebound effects. The first examines the relationship between reducing traffic congestion and mass transit. Traditionally, the solution to traffic congestion has been one of supply and demand, and new roads are built to accommodate the increase in vehicle traffic. But, notes Sterman, augmenting road capacity just does not work: When new capacity is added, new vehicle trips, or longer ones, are encouraged. These trips quickly fill up the new road capacity, which produces a spiral of more severe traffic congestion. Meanwhile, some portion of these new auto trips come at the expense of public transit, which, upon losing riders, then reacts by either cutting service, or increasing fares. This downward spiral of public transit has a feedback loop which increases the attractiveness of driving. Sterman observes that planning is chaotic if we don’t pay attention to these feedback loops and really think through what it is peopl...