While the map doesn't include information on air travel, it provides data on all surface level transport, including roads, railways, rivers, and land cover types. Roads, the researchers say, are “the primary driver of accessibility globally”.
"The game-changing improvement underpinning this work is the first-ever, global-scale synthesis of two leading roads datasets – Open Street Map (OSM) data and distance-to-roads data derived from the Google roads database," Weiss explained in a statement.
Eight out of 10 people live within an hour's traveling distance of a city, but there is a huge gap in accessibility between high-income countries and low-income countries. Whereas 90.7 percent of people in high-income countries (the majority in North America and Europe) can reach an urban center in less than an hour, only 50.9 percent of those in low-income countries (which are concentrated in sub-Saharan Africa) can do the same.
Even within countries, the project reveals a link between household wealth/education status and proximity to cities, with wealthier, educated citizens enjoying better access.