When I started writing about urban planning and related subjects, I thought we had these things called cities, towns and neighborhoods and that we figured out how to get around, between and among them. Now, I realize that we figure out how to get around and that creates these things called cities, towns and neighborhoods, as well as all their assorted kin--subdivisions, shopping malls and office parks.

Places are born out of transportation. By moving, we invent ways to stand still. When we make a decision about transportation, we also decide how to live. That's why, in writing about transportation in this new column for Governing, I'll be less inclined to tell how a car, train or bicycle functions then to understand how a means of transportation affects the world around it.

The history of cities and their component parts is really a history of transportation. Early ports created port cities. Railroads created railroad towns. Early roads created the first automobile suburbs, and the first super-highway created the first regional shopping mall. Our transportation choices set the structure for how places look and function.

Building the Erie Canal in 1817 established New York as the nation's premiere city by making it the commercial gateway between the Old and New Worlds. In more modern times, a huge airport and six intersecting interstates helped make Atlanta the capital of the South--and the capital of sprawl. On a more delicate scale, the first streetcar lines in the late 19th century produced the much beloved neighborhoods of narrow townhouses and small apartment buildings on tree-lined streets. You can see this legacy in cities all over the United States, even though layers of pavement usually hide the old streetcar tracks.

In government circles, there is a tendency to relegate transportation decisions to the engineers. This is like an army giving away its bullets. In a more effectively organized government, a department of urban design or planning would supervise agencies of transportation. Because this isn't usually the case, planners often end up dealing with the effects of transportation decisions rather than helping make them in the first place.

When developers build subdivisions today, the pattern of the street system--and whether bike lanes or walking paths are included--will shape the neighborhood's character far more than the architectural style of the homes that are in it. Sometimes, as with a suburban subdivision, private interests take direct control of transportation decisions. But usually they take a back seat to public officials, both elected and appointed.

Government typically plays the most important role in transportation because the scale required for effective action, both in land area and capital, is so large. Although private companies sell or rent space in automobiles, planes and trains, government builds or massively subsidizes the roads, airports and tracks. And for transportation to work, it has to add up to a coherent whole. As one transportation engineer said, "transportation is a system. You can't have a little bit of transportation."

Lewis Mumford, that late great writer on cities, wrote an essay a half-century ago called "The Highway and the City," in which he asked the question: "What is transportation for?" That's still the right question, especially when answered in its fullest sense.

Often, when we are deciding to build a new highway or train line, we think only about unclogging the most irritating traffic jam. That is shortsighted. In the 1950s, prescient observers such as Mumford realized that when we committed to building the interstates, we would also create a new type of living built around the highway and automobile.

This is an old pattern. In 1904, when New York City opened its first subway line, few realized that it would help produce a new building type called the skyscraper, made possible by allowing thousands of people to travel to and pack into a single tall building without carrying a car or carriage with them.

People argue fiercely over transportation, ranging from neighborhood activists protesting a planned street widening, to lobbyists battling it out over airline or Amtrak subsidies. Transportation shapes neighborhoods and economies, so people care about it. If I advocate for anything in this column, it will be that we make our transportation decisions more consciously.

M.F.K. Fischer, who wrote about the pleasures of the palate, was able to show the world through her portraits of a creamy bowl of soup or a crusty loaf of bread. "Consider the Oyster," she began one of her books. Seen in the right light, you can also show the world through a train station, an airport or a left-turn lane. "Consider the off- ramp," I ask of you. "Consider the curb cut."