Values of travel time enter the appraisal scheme both as values for modelli
ng and forecasting and as values for use within project evaluation. This pa
per considers whether and how travel time values should be used within eval
uation. The basic theories of private and social travel time valuation are
set out. Issues such as the valuation of working time savings, the case for
segmenting values by journey purpose and length, sign and size of time sav
ings and mode of travel, and the income elasticity of the value of time, ar
e reviewed. Two of the main conclusions are that time is a scarce resource
and should be valued but that direct use of willingness to pay values is in
appropriate for social appraisal of projects. Some form of social weighting
scheme is required. (C) 2001 Elsevier Science Ltd. All rights reserved.