The automobile allowed us to spend the 20th century spreading out in all directions.

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American settlement patterns have always been strongly influenced by our transportation technology. In 18th century America, the best locations for cities and commerce were accessible to major rivers and ports. Few people lived in "backwater" communities. Once you got off the boat, however, you had to rely on the power of feet -- human or horse. Within cities, all activities had to be located within walking distance of each other. Suburban growth extended about as far as one could go within a day's ride from town.

With the advent of steam- and diesel-powered trains in the 19th century, people began venturing away from the rivers and built new cities across the landscape. However, since foot-power was still the dominant form of local travel, rail towns retained the compact form of older communities.

The automobile allowed us to spend the 20th century spreading out in all directions. Networks of high-speed highways and local roads created opportunities to build cities virtually anywhere. With the power of hundreds of horses under the hood, cars made it possible for people to live miles away from daily activities such as work, school, and shopping. No longer confined to the walkable dimensions of one-horse towns, we shaped new communities around large street networks and parking lots.

As the 21st century dawns, the American dream made possible by the remarkably fast, flexible mobility of the automobile has begun to take on nightmarish qualities. It is becoming clear that our collective dependence upon the automobile is threatening our natural environment, our health, and our economic vitality.

As our anxiety about these problems grows, however, so does our creativity. We are in a time of fundamental change that portends both danger and opportunity.

Our Natural Environment

A 2009 report by the U.S. Environmental Protection Agency indicates that fossil fuel combustion for transportation is responsible for a third of America's CO2 emissions, which are an important ingredient of the "greenhouse gases" associated with global climate change. The three most prominent factors affecting the transportation sector's emissions are the fuel economy of vehicles on the road, the types of fuels used, and the overall amount of driving by all vehicles, expressed as vehicle miles traveled (VMT).

Federal agencies, state governments, and private sector entrepreneurs are working on the tasks of making vehicles more energy-efficient and finding new sources of fuel. But our success at reducing VMT depends largely upon our ability to plan and locate communities in ways that reduce our need to drive. To achieve this goal, it is essential for local and regional planners and decision-makers to redesign existing and new places so that people can choose to walk, bike, or use transit for daily trips.

Studies show that improving the proximity and connectivity of activities can reduce the overall number of vehicle trips generated within a given area by as much as 25 percent. This, along with operational improvements to improve free-flow movement on local roadways, can make an important contribution toward reducing the amount of carbon dioxide generated.

Stormwater runoff is another important environmental problem exacerbated by our automobile-oriented development pattern. That's because roadways, surface parking lots, and driveways result in large amounts of paved, impervious surface which, in turn, can lead to excessive runoff.