Assessing travel time reliability in transport appraisal

This paper considers a way of assessing travel time reliability in transport appraisal. The term travel time reliability generally refers to variations in journey time that travellers may not predict. Two essential requirements for the evaluation and guidance of the appraisal are discussed. The requirements represent the measurement and valuation of travel time uncertainties. The gap between actual and planned journey times is used for the quantification, subject to the differing characteristics of road and rail usage. A logit-based choice model is developed to derive monetary values of travel time variation. Guidelines are established using the standard framework of the rule of a half. Concluding remarks are also presented.