System cost-based multi-criteria analysis for urban transport solutions

Solutions for urban transport problems tend to be mode-specific interventions. These could be improvements to an existing mode or the introduction of a new mode. In undertaking the feasibility study of such interventions, it is usual to consider the costs with benefits to users of that mode of transport only. However, the impact of change in one mode, on the demand and the supply of another mode and indeed on the entire urban transport system is often overlooked due to the complexity involved in understanding and computing such effects. This paper investigates the impact of an urban transport intervention in terms of the contribution it makes to the total economic cost of the transport system measured in terms of user time costs and vehicle use cost of all modes in the transport network of the urban area. This allows the evaluation of the economic impact of highway projects on public transport operations and vice versa, as well as one public transport project on another. The economic assessment of an intervention is made using benefits-cost analysis (BCA) by comparing its investment cost over the design life with the resulting system benefit which is considered as the value of the net reduction in total transport system cost. Two supplementary measures of environmental affability and user attraction are used as criteria for extending economic BCA to incorporate non-quantifiable parameters using multi-criteria analysis. The application of this methodology has been illustrated with a case study of the Galle Road Corridor in Colombo, Sri Lanka.