Road Trip: America's Most Paved Places

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Along with being the nation’s capital, Washington D.C. leads the country when it comes to pavement: It has the least amount of open space between roads of any U.S. county.

By contrast, the study finds that Keweenaw County in Michigan offers the most room between the roads of all U.S. counties.

Counties with the least space:

  • Washington, D.C
  • Saint Louis City, Missouri
  • Kings County (Brooklyn)

Counties with the most space:

  • Keweenaw County, Michigan
  • Saint Bernard Parish, Louisiana
  • Terrebonne Parish, Louisiana

With more than 4 million miles of roads in the United States, the farthest you can venture from a road is 22 miles (unless you’re wandering around Alaska or the swamps of Louisiana). The only place you can be 22 miles away from road in the contiguous states is a spot in the southeast corner of Yellowstone National Park in Wyoming.

Roadless space

Roads are critical to providing people with access to natural resources and services like stores, schools and hospitals.

“Roads are really the life-blood of our economy,” said study team member Raymond Watts of the U.S. Geological Survey in Ft. Collins, Colo. “They’re the circulatory system of our culture.”

But just as negative space on an artist’s canvas can be as important as the painted portions, the space between roads, or roadless space, can be just as critical. The amount of roadless space in an area is a good measure of how rural that area is, and so measurements of this space could help city planners measure sprawl as a city grows.

Road-free areas are also critical to maintaining ecosystems, as traffic affects nearby plants and wildlife, so knowing road density could help conservation efforts.

A new measurement

Watts and his colleagues came up with a new way to measure roadless space that is “unarguable and umambiguous,” he said.

They recognized that current calculations of roadless space weighted an acre of land 1 mile from a road the same as one 10 miles from a road, when the latter acre arguably has 10 times as much value in terms of roadless space.

By looking at a mosaic map of U.S. roadways, the researchers found the distance to the nearest road at points in every U.S. county, and substituting that value for elevation, the researchers created what Watts calls a “synthetic topography.” The higher the “elevation” is for a point, the more remote it is.

While this method, detailed in the May 4 issue of the journal Science, is a base to start on, other factors will eventually need to be taken into account, Watts said, including type of road (highway vs. dirt), traffic volume on a road, distance of a point from every road around it and how accessible the road is from the terrain around it.

As Watts pointed out, the distance from one road to another across a canyon may not be the best measure of roadless space, as the canyon can’t be easily traversed.

Andrea Thompson
Live Science Contributor

Andrea Thompson is an associate editor at Scientific American, where she covers sustainability, energy and the environment. Prior to that, she was a senior writer covering climate science at Climate Central and a reporter and editor at Live Science, where she primarily covered Earth science and the environment. She holds a graduate degree in science health and environmental reporting from New York University, as well as a bachelor of science and and masters of science in atmospheric chemistry from the Georgia Institute of Technology.