Forecasting air traffic demand for major infrastructure changes

The paper provides a review of traffic forecasting methods and compares the predictions generated by using different quantitative methods based on a case example from a planned Norwegian airport. The paper focuses particularly on two forecasting methods. The case airport exemplifies how analogies as a forecasting method might be better suited than elasticity methods for studies of major changes in infrastructure. The difference in traffic forecasts will depend on the methodological approach chosen and some generic considerations are given on this topic. In the studied case, we find that the airport project has a negative net present value when the lowest traffic forecasts are used and a positive net present value when the highest traffic forecasts are used. Hence, the inability to draw unambiguous conclusions would be confusing for decision-makers when deciding on whether to build the airport.