This paper tests the elasticities to time, frequency and interchange implied by an approach which combines these three variables into a single term and compares this approach with models which estimate separate elasticities. The forecasts obtained from different model forms can be appreciably different

The authors formulate and estimate a model of international air travel demand for Israel. Consumers’ wealth is found to be a significant determinant and failure to include it in the estimated equations yields price elasticities which are biased downward and income elasticities which are biased upward.

It is concluded that aggregate approaches to forecasting demand may be appropriate for cheap investments, such as new stations, or an initial assessment of a wide range of options. For detailed consideration of expensive investments, such as new rail services, disaggregate methods based on RP and or SP data should be considered.