The effect of grid size on street location time in maps

Two experiments investigating the time taken to locate roads in an urban map are described. The data support the hypotheses that road location time is (a) linear on the reciprocal of the distance between grid lines, and (b) linear on the number of roads per grid square. The issue of the optimal distance between grid lines is discussed and it is argued that for the particular map investigated, this distance should represent 0·25 km.