This paper provides an overview of the state of some of the demographic and economic factors influencing the forecast of the future state of passenger flows in international traffic on the railway line from Belgrade (SV) to Bar (ZPCG). In addition, it presents mathematical models of linear single and multiple (two-factor) regression that are proven to be authoritative for forecasting the future volume of passenger transport in international railway traffic on the line Belgrade (SV) - Bar (ZPCG). The parameters of the model evaluation in terms of the accuracy of forecasting the future volume of transport on the observed railway line are also presented.