Monthly Archives: June 2007

Fun with Density and Transit Statistics

Conventional wisdom holds that the U.S. is too spread out for workable mass transportation except in a few high-density cities. Urban planning expert Anthony Downs offers this explanation:

But in 2000, at least two thirds of all residents of U.S. urbanized areas lived in settlements with densities of under 4,000 persons per square mile. Those densities are too low for public transit to be effective. Hence their residents are compelled to rely on private vehicles for almost all of their travel, including trips during peak hours.

Traffic: Why It’s Getting Worse, What Government Can Do

Is that accurate? It all depends on statistics and assumptions, both of which are endlessly susceptible to manipulation. For instance, Downs uses “settlements” as the geographic unit of analysis and calculates how many Americans live below a certain density threshold.

That’s one approach, but there are many different approaches. We could use other geographic units and find out the average density in each of them.

Geographic Unit Population Population
% of U.S.
Land Area
(sq mi)
Land Area
% of U.S.
United States 281,421,906 100 3,537,438 100
Metropolitan Areas 225,981,679 80.3 705,790 20
Urbanized Area 192,323,824 68.3 72,022 2

Source: U.S. Census 2000

Looking at the entire United States, what impresses is the vastness and diversity of the land. It’s the America of spacious skies, amber waves of grain, and purple mountain majesties; of trackless tundra, sizzling deserts and rocky badlands.

But look at the urbanized area of the nation and a different picture emerges. Sixty-eight percent of Americans live on just 2 percent of the U.S. land area. Seen in this light, the large majority of the U.S. population is remarkably concentrated on the land. What implication does this have for population density?

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Connectivity Part 6: Vehicle Miles and Traffic

This is part 6 of a series. See also IntroductionHistorical BackgroundLatter Half of the 20th CenturyNeighborhood WalkingNeighborhood CrimeCrash Safety

Automobiles have brought many benefits to society, and at the same time there are many good reasons to reduce the number of vehicle miles traveled (VMT) each year. Thoroughfare connectivity is part of the strategy that reduces VMT; it is a necessary, but by itself insufficient, component of walkable environments. Also, well-connected thoroughfares can reduce traffic congestion by providing alternate travel routes, and can speed emergency services by providing more direct routes and better accessibility.

There’s a nascent movement to advance better-connected thoroughfares, but meanwhile the inertia of preexisting standards and regulations discourages or prohibits high connectivity for most new construction. In addition, NIMBY residents are frequently opposed to new street connections. Future trends in energy, environmental and cultural conditions, however, could lead to walkable, well-connected thoroughfare layouts becoming more customary.

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