This paper compares forecasted effects of the Stockholm congestion charges withactual outcomes. We show that the transport model was able to predict thecharges’ effects on travel demand reasonably well, but with someunderprediction of the effect on leisure trips. The most important concernsduring the design of the congestion charging scheme were traffic reduction inbottlenecks, increase in public transport ridership, decrease of vehicle kilometresin the city centre, and traffic effects on circumferential roads. All of these factorswere predicted well enough to allow planners to draw correct conclusionsregarding the design and preparations for the scheme. The one majorshortcoming was that the static assignment model was unable to predict thesubstantial effects on travel times. We conclude that the transport model workedwell enough to be useful as decision support, performing considerably betterthan (unaided) “experts’ judgment”, but that results must be interpreted takingthe model’s various limitations into account. The positive experiences from theStockholm congestion charges hence seem to be transferable to other cities in thesense that if a charging system is forecasted to have beneficial effects oncongestion, then this is most likely true.
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