The implications of alternative road pricing systems for public transport and for the equity of road travellers

Road pricing has frequently been proposed as an effective means for tackling congestion and reducing environmental impacts caused by the increasing demand for car travel. However, there has been strong public and political opposition to the introduction of road pricing.. One major concern is uncertainty about the equity implications of pricing for travellers. In this paper we consider the equity implications of four road user charging systems, taking account of potential benefits for public transport. The four charging systems considered are cordon- and distance-based pricing, both of which levy fixed charges for any given trip, and time- and delay-based pricing, where fees vary due to the travel conditions encountered. This paper is a natural succession to two earlier studies on road pricing due to May et al (1994) and Smith et al (1995). In these two studies the extent of benefits in network conditions due to road pricing were assessed without giving considerations to public transport and the equity of road pricing. Using two well-established models, SATURN and CONTRAM, to represent detailed network effects of charging in two real cities, Cambridge and York, this study has focused mainly on: 1) the degree to which benefits in network conditions due to road pricing, found by the previous studies on road pricing, aid the performance of public transport; 2) the equity implications of road pricing for car travellers alone; and 3) the combined equity implications for all road travellers, including public transport travellers. The aim in 1) was to estimate the overall efficiency gains for public transport which are likely to arise from each of the four charging systems (including delay-based charging which appears to achieve the best delay reductions). In May et ai (1994) we found that by using delay-based charging total queueing delay in Cambridge may be reduced by 70% with quite modest charge levels. Such sharp reductions in queueing delay are likely to have a major impact on buses, since buses spend a high proportion of their travel time in traffic queues. The concern in 2) was to assess how costs (including charges paid) and benefits (including reduced travel times) are distnT~uted among car travellers who may be expected to value time savings differently (without considering public transport). In 3) the aim was to assess the effect of road-use charging on overall efficiency and equity in the presence of public transport. Bus performance is very sensitive to congestion and so the substantial reduction in congestion brought about by delay-based charging should improve (i) overall network performance and (ii) beth the lot of the better-off car driver and also the lot of the worse-offbus traveller. In addition to 1), 2) and 3) above, in this study we also performed sensitivity tests to make sure that the gains estimated in our previous study, in this study, and in other studies, do not depend unduly on the assumptions built into the models used to generate the results. The rest of the paper is divided into four sections. In section 2, we give the modelling assumptions made in the course of this study. In section 3 we describe the way the focus points 1), 2) and 3) above were accomplished. Then in section 4 we provide the results of this study. Finally section 5 concludes the paper