Demand forecasts are the basis for socio-economic and environmental appraisal of major infrastructure projects. Furthermore, estimates of the financial viability of projects are heavily dependent on the accuracy of such forecasts. According to the experiences gained with the accuracy of demand forecasting in the transport sector, covering traffic volumes, spatial traffic distribution and distribution between transport modes, there is evidence that demand forecasting – like cost forecasting, and despite all scientific progress in modelling – is a major source of uncertainty and risk in the appraisal of major projects.

Channel tunnel, Great Belt and Øresund

The Channel tunnel opened operations in 1994. Traffic forecasts made at the time of the decision to build the tunnel predicted 15.9 million passengers on the Eurostar trains in the opening year. Actual traffic in 1995, the first full year of operations, was 2.9 million passengers, or 18 per cent of passengers predicted. After more than six years of operations, in 2001, the number of passengers had grown to 6.9 million, or 43 per cent of the original estimate for the opening year (see Figure 3.1). Total passenger traffic (including passengers on shuttle trains, in addition to Eurostar trains) was predicted at 30 million for the opening year; actual total passenger traffic in 1997 was half of this. Rail freight traffic was predicted at 7.2 million gross tonnes for the opening year; actual rail freight traffic was 1.3 million gross tonnes in 1995, or 18 per cent of freight predicted.