Where are the World's Straightest Roads?

According to this map the world's straightest roads are in the American Mid-West and the Canadian prairies. How Straight or Bendy are the World's Roads is a Leaflet powered map showing the straightness of the world's roads (or at least all the roads that have so far been added to OpenStreetMap).

Each road on OpenStreetMap has been given a 'bendyness ratio', which was calculated by dividing its length of the road by the straight line difference between its end points. The map is divided into equal sized squares. Each square on the map is then colored by the straightness of all the roads in that square.

North America seems to have the world's straightest roads. The Netherlands and northern Germany also seem to prefer their roads to be of the straight variety.