Comparison of judgmental and optimal road pricing cordons

The performance of cordon pricing schemes is critically dependent on the location chosen for the cordon, and the toll imposed. Most cordon designs have been based on professional judgment, in the absence of guidance on the principles of efficient design. In this paper, a methodology based on Genetic Algorithms has been developed to identify the optimal location and toll level for one or more cordons, for a given objective function, with or without constraints on the design or required outcomes. To compare the performance of judgmental and optimal cordon designs, the method has been tested on a network of Edinburgh, with optimisation designed to achieve welfare maximisation with and without constraints on desired level of revenue and equity impact. The methodology is shown to generate appropriate solutions to all of these problems. The optimal single cordon achieves welfare benefits which are double those of the best judgmentally designed cordon. Constrained optima inevitably achieve lower benefits, but it is possible to design them so that this loss is minimised.