Fourth, ex-post studies of rail investments confirm the importance of timetable assumptions, concluding that they are essential for demand forecasts and thus for social benefits, and an important source of forecasting errors. For example, Tegnér(2001) concludes that the optimistic timetable(high frequencies, low fares, short travel times) used in the demand forecast for the Ostkustbanan railway line was a major reason for a fourfold over prediction of increase in demand. SIKA (2000) found that the actual number of travelers on three studied Swedish railway lines was over-predicted with between 26% and 72%, quoting wrong timetable assumptions as one of the reasons for the demand shortfall. Olsson (2006) and Mackie and Preston (1998) also point out that the accuracy of the calculated benefit of rail investments relies on the assumptions of the realized timetable.