THE SENSITIVITY OF TRANSPORT INVESTMENT BENEFITS TO THE EVALUATION OF SMALL TRAVEL-TIME SAVINGS

Abstract

This paper investigates the implications of different conventions for evaluating small travel-time savings in transport investment benefit calculations. In a series of network simulations, the extent and composition of time benefits of different length, arising from a set of highway policies, are computed. Two alternatives are examined in detail: that in which travel-time savings below a critical threshold are given a zero value, and that of liner discounting below a threshold level. These are compared with a widely adopted convention in which a constant unit value of time is taken to evaluate user benefits. The implications for investment appraisal are considered.