In spatial analysis, network deviousness is the discrepancy between the lengths of the actual routes in a network and the straight-line distance between the places linked up. For any pair of places on the network it can be measured by the detour index. The detour index is a measure of how directly movement may be made on a network. It is calculated as the ratio of the shortest actual route distance between a given pair of nodes and the direct, straight-line or geodesic distance between the same two points.