Sensitivity analysis of welfare, equity, and acceptability level of transport policies
Transport planners face a major challenge to devise policies to meet multiple expectations and objectives. While we know that transport networks are complex, multi-modal and spatially- distributed systems, there is now a long history mathematical tools that assists planners in understanding travel movements. However, the objectives that they are asked to achieve do not always admit such a quantification, and so there is a potential mismatch between seemingly qualitatively- driven objectives and quantitatively expressed models of the transport system. In the present paper we address this mismatch, by focusing on three objectives that we believe represent the typical interests of a planner. These are namely: is the policy economically justifiable (efficient), is it 'fair' (equitable), and is it justifiable to a democratic society (acceptable)? We provide mathematical representations of these objectives, and link them to mathematical theory of transport networks, in which we may explore the sensitivity of travel behaviour (and hence the objectives) to various multi- modal transport policies. The detailed steps for representing the policy objectives and sensitivities in the network are set out, and the results of a case-study reported in which road tolls, road capacities and bus fares are the policy variables. Overall, the paper sets out a systematic method for planners to choose between multi-modal policies based on these three objectives.