The US road network of the is one of the largest
human-made constructions on Earth. The 4 million mapped roads take
up about 1 per cent of the nation's land area – about the size of
South Carolina. So what would a country look like if the only
information you had about it was its road network – no coastal
outlines or mountain ranges allowed?
This is the kind of question that fascinates data manipulator
and computational designer Ben Fry, who is based in Cambridge,
Massachusetts. Using 2006 US census data, he built such a map.
He found out that you can't suppress the geographical features:
they appear as the roads avoid them, and you can get a more
immediate idea of the population density of a region just by
looking at its roads than by studying its population data. He says
the roads also give insights into the history of a place: "You can
see an incredible range, from the highly regular roads around
Kansas City, for instance, to the haphazard, like immediately
outside the Bay Area on the West Coast," which reflects how the
network was built up over time.
It wasn't just physical insights Fry gained from his map, but
also some "interesting titbits" about the American psyche. For
example, the top 10 street names are pretty much the same in every
state, and roads are often named after trees even when no specimens
exist for hundreds of miles: "'Magnolia' is such a nice-sounding
word, town developers don't mind that it has no local relevance,"
he says.
The US Geological Survey (USGS) has interpreted similar
information in another way. Using census data from 2000, they have
created a map of the country, coloured according to the distance
from fixed points to the nearest road, with data points every 30
metres. The green patches indicate areas where the nearest road is
10 to 20 kilometres away, and the yellow spots where a road can be
found less than 100 metres away, with a spectrum of blue hues in
between.
On both representations the areas with the most roads tend to
appear in cities, but exceptions include the oil and gas fields of
west Texas, where dense road networks have been built to export the
raw materials. The areas with the least roads correspond to
inaccessible landscapes or places where there is little economic
motive to build them: for example, the sand hills of Nevada, the
deserts of Arizona, New Mexico and California, the swamps of
southern Florida and the steep slopes of the Rocky Mountains.
Fry's map was put together mainly out of curiosity, but the USGS
says that its map will be used as a resource for "comparing
landscape patterns manipulated by humans with natural
patterns".