Introduction

The original intention behind this study was to analyse who would receive the benefits and who would bear the costs of the Greater Glasgow Transport Study (GGTS) recommended plan (Tippetts, Abbet, McCarthey and Stratton 1967). This plan was recommended on the basis that it would minimise social costs (the combination of capital, maintenance and user costs), however no consideration was given to the distribution of costs and benefits resulting from the proposals.

Having studied the output from the GGTS transport model, it was found that it could not be disaggregated effectively, which would be required, if the distribution of costs and benefits was to be found. It was also considered that this type of study is of little use to the politicians who make the decisions on the transport plan. What would be of more use is a method which could be used in future evaluations.

It was then decided that an attempt should be made to design a new transport model and evaluation procedure in the light of existing deficiencies in transport studies, particularly the lack of equity considerations in the evaluation, using the GGTS as a case study. However the existing deficiencies threw up so many problems that further analysis of the GGTS and the production of a new model was not possible.

The main problem, of those encountered, is the use of the Kaldor-Hicks criterion[1] , for the identification of an improvement, in cost-benefit analysis. Linked to this is the conceptual problem, that an infinite number of different distributions of costs and benefits can produce the same net benefit, so consideration of distribution can not be encompassed satisfactorily by cost-benefit analysis, which is based upon the maximisation of the single function of net benefit.

Other problems are due to the lack of consideration of the effect of the level of provision on 'demand', and the lack of consideration of different possible land use patterns. These and other problems if tackled would remove the practicability of comparing any improvements with the 'do-nothing' case upon which the calculation of costs is based. Another problem is due to the lack of explicitly stated objectives in transport planning. The use of cost-benefit analysts as the sole criterion upon which plans are chosen raises the objective of 'economic' efficiency to one of overriding importance.

Consideration and evaluation of any other objectives in transport planning would remove cost-benefit analysis from its present dominant position. It would also pose serious problems of how to trade off one objective against another.

In the light of the problems encountered, a tentative new evaluation procedure is put forward. However it is still prone to many of the deficiencies of existing methods.

The contents are arranged to correspond to these deficiencies. In the first section an example is given of the methodologies presently used in transport planning and cost benefit analysis. In the second the reasons why equity should be considered in evaluation, and a method for doing so, are put forward. The third and fourth sections deal with many of the problems and deficiencies of present transport planning and cost-benefit analysis methodologies. The fifth section gives an account of how these and other problems affect the proposed method for considering equity.

A further problem that was encountered is that caused by the use of average values in numerical modelling. This problem is not confined to transport models. It is fully explained in the Appendix.

[1] This criterion maintains that any change which produces a net gain is an improvement, even if some people suffer an uncompensated loss.