1. A computer-implemented method for generating a map for display, comprising: receiving a plurality of GPS samples from a plurality of GPS devices, each GPS sample comprising a location, a direction of travel and a speed of travel of a GPS device from which the GPS sample is received; associating selected GPS samples with respective road segments on a map based on the location and the direction of travel in each selected GPS sample; identifying a turn restriction on a road segment of the map based on a plurality of directions of travel from GPS samples associated with the road segment; and generating, for display, a map containing the road segment, the road segment labeled with the identified turn restriction.