Modifications of the Stockholm congestion pricing scheme and effects on different user groups

This paper analyzes how different user groups are affected by changes to the present congestion pricing scheme in Stockholm. The Stockholm congestion pricing scheme has shown that pricing of transport systems can reduce congestion and increase accessibility in the city centre. The pricing scheme can however be improved when it comes to ability to mitigate congestion without unnecessarily affecting user groups whose contribution to congestion is minor. A large number of theoretical studies have been made on equity effects of congestion pricing. Eliasson and Mattsson (2006) extend the theoretical literature with a quantitative methodology for evaluation of equity effects of real-world pricing schemes. In the mentioned paper, Eliasson and Mattsson conclude that analysis of equity effects have to be carried out for specific cities and specific congestion pricing and refund schemes to be able to draw any conclusions on whether a congestion pricing policy is regressive or progressive. We study effects of modifications of the congestion pricing scheme using a recently developed dynamic transport model for Stockholm called SILVESTER. Choice of departure time is modeled in SILVESTER, which is very important (but often omitted) since both congestion and the charge one has to pay is time-dependent. Car travel times and time spent in queues are calculated using mesoscopic traffic simulation. SILVESTER models car users, but they can switch to public transport, which makes it possible to evaluate the mode switch effect induced by a specific congestion pricing scheme. Possible modifications to analyze include changes to charged amounts, timetable and locations where the charge is levied. Regarding user groups, this paper analyzes effects for three different group categories: income, household type and occupation. SILVSTER allows for analysis of how costs and benefits are distributed across origin-destination-pairs and trip purposes. In order to compare costs and benefits for user groups, the share of trips that each group performs are calculated per origin and trip purpose. Furthermore, the effects of congestion charges for different user groups are, to a large extent, dependent on how revenues are used. This paper therefore also compares two refund strategies: lump-sum and improvement of public transport.