When a route is planned, the distance of route and earthwork volume have an important role as an economic factor. In this paper, an investigation is made on the selection of optimum route with respect to two factors above mentioned. For this investigation, a numerical test is also executed to two different types of terrain, i.e. terrain with constant slope and no undulation and terrain with slope and undulation. The results show that the shortest route is determined by the degree of undulation with no relation to the slope of topographic model, and the earthwork volume is affected by the amount of undulation and interpolation function.