The Science magazine website is by subscription, but the abstract of the study, Roadless Space of the Conterminous United States, notes that the authors have created a new way to measure roadlessness:
We introduce a metric, roadless volume (RV), which is derived from the calculated distance to the nearest road. RV is useful and integrable over scales ranging from local to national. The 2.1 million cubic kilometers of RV in the conterminous United States are distributed with extreme inhomogeneity among its counties.The map image above shows RV by County. The scale ranges from high RV areas, shown in blue, where there are more areas without roads, to low RV areas, in red, where there are more roads.
Discovery News presents a longer overview of the study (Roadless Space Uneven Across U.S.) which discusses the relationship between this new measure of roadlessness and habitat fragmentation, and notes that the study found that, in some areas, we seem to build roads in the wrong places:
And when the scientists compared the roadless space with the number of people in a given area, they sometimes found a mismatch: that is, too many roads for too few people.The study's abstract, by the way, offers a lovely example of scientific obfuscation. That poetic phrase "distributed with extreme inhomogeneity" means, I think, "not in any regular way that this highly trained scientist can see."