Population density is one of valuable factors of economic development and ecological stability in inhabited areas. Classic approach to direct estimation of the population density is the application of gravity model to the settlement. The distance in the model is estimated usually as a straight-line distance between settlements. Our study is devoted to implementation of gravitational model able to account distances in transportation network. This model is demanded when investigating transborder regions, where people migrations through the state border are possible at checkpoint locations only. We use the ArcGIS software to ensure settlement field potential computations and mapping, and Valhalla open source routing engine to build routes and compute distances. Current results of our study incorporates the data conversion and processing methodology, a set of algorithms (program code) that implements these techniques, and a map series produced for the Russia-Kazakhstan transborder region that illustrates performance of elaborated methodology.