Highway appraisal under uncertainty.

This paper presents, in outline, an approach to the comprehensive analysis of the effects of uncertainty in road planning and appraisal. The most obvious source of uncertainty is the future traffic demand and the approach relies on the estimation of the uncertainty of the traffic forecasts, by a careful analysis of the uncertainties associated with the use of a traffic model. The output of the analysis is a representation of the forecasts of future traffic flows on the road network in the form of probability distributions.