Equity measures and their performance in transportation

This paper aims at equity implications of transportation policies by using a range of equity measures in two case studies. Different measures of inequality embrace different normative judgments. Early studies have warned about placing too much trust in a single measure. One approach is to address equity considerations by assuming an explicit form of social welfare function and the choice of a desired inequality aversion parameter. A second approach is to apply an inequality measure to a given pair of distributions of a variable (e.g., income and accessibility) that changes as the result of a policy. The latter approach is adopted in this paper. A partial equilibrium model of transportation is used for the calculation of the changes in income, accessibility, and the net benefit for different social groups. This paper demonstrates the challenges that arise in addressing equity with a partial equilibrium model of transportation. An overview of some equity measures and their properties is provided first. The performances of these equity measures are evaluated for alternative road pricing schemes for Oslo, Norway. The paper illustrates that relating the equity objective to a predefined value of any of these measures is not desirable. It is difficult to make a judgment about the equity implication of a policy on the basis of a single measure and without a thorough examination of several measures. The paper also shows that the sizes of the equity measures are quite sensitive to the level of spatial disaggregation.