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What Are The Implications For Other Themes?

Based on the results and conclusions above, we find that there are many links between the environmental perspective on RUC, and themes discussed elsewhere in this report.

• Objectives: Environmental effects should be considered when objectives are formulated for a charging scheme.
• Scheme design: Environmental ambitions should affect the design of the scheme in terms of type of scheme (toll ring, zone), location of cordon and control stations, level of charges, variability of charges, and potential exemptions.
• Technology and Business systems: Potentially, technology could be developed to allow for registration of vehicles with respect to environmental features (which in turn would open for more differentiated charging). However, the typology of official vehicle registrations will limit the possibilities for such differentiation.
• Prediction: The prediction of environmental effects requires several additional models to those needed for the prediction of volume and congestion effects. To be able to assess a suggested charging scheme with respect to its environmental consequences, we should ideally be able to predict speed variation and noise as a function of volume, emission factors as a function of speed profiles, air quality (concentrations) as a function of emissions, immissions (affected population) as a function of air quality and noise, and health effects as a function of immissions. For several of those modelling steps, relevant relationships are yet to be identified, and models are yet to be developed. Further, the “reverse” relationship between environmental quality and road user behaviour is also of interest – e.g. the effect of improved air quality on the propensity to walk or cycle (creating secondary health effects), and the effect of improved urban quality on customer behaviour (influencing economic consequences of charging).
• Traffic effects: The central factors that determine the positive environmental effects of charging are (in order of importance):

i. An overall reduction of traffic volumes
ii. Reduction of traffic where there are a lot of people and in densely built cities
iii. Reductions in flow of particularly polluting vehicles
iv. Smoother traffic flow.

Thus, traffic effects are necessary building blocks for any achievement with respect to environmental objectives.
• Economy: All aspects of environmental quality will affect the attractiveness of the city centre as a shopping, living and working environment. In turn, area attractiveness will affect demand in the retail sector, demand for housing and the balance at the job market. These processes will all have a positive effect on the profitability of economic activities in the charged area. This may (to some or all extent) compensate for those potential negative effects of higher travel and transport costs that are often feared by representatives of affected businesses.
• Equity: As for any effect of RUC, political interest and concern over environmental consequences will not be only about average (or total) effects. Focus will also be on how those effects are distributed over the population. In particular, there is reason to study the effects with respect to environmental justice, so that charging does not contribute to further increasing the proportion of environmental pressure carried by the less privileged.
• Appraisal: Environmental effects should be considered as an integral part of a multi-criteria appraisal. Relevant values of health effects and other environmental consequences have not yet been researched to an extent compared with elements traditionally regarded as important in appraisal such as the value of- time. Also, it must be borne in mind that the appraisal of environmental effects is subject to fundamental uncertainty linked to the problems of how risks and (very) long-term effects should influence decision making.
• Acceptability: As was pointed out in Section 8.4, the expected environmental effects play an important role for public acceptability of a proposed charging scheme. Failing to analyse the environmental aspects of a charging policy may well prohibit its implementation altogether, even if that policy is suggested and designed from a congestion perspective.
• Transferability: Environmental effects seem to be rather consistent between case studies of URUC. Thus, there is reason to believe that current knowledge concerning the environmental field, would be transferable to other future schemes as well.
• Implementation: Anticipated environmental improvements may well be an important element in gaining acceptance of a proposed road user charging scheme. It will be important in the implementation process to ensure that these benefits are realised. Depending on the level of traffic reduction, it may be possible to obtain further environmental improvements after implementation, by focusing traffic on less sensitive streets.
• Evaluation: Emissions, as well as concentrations and immissions, can hardly be measured in real traffic. Therefore, they have to be predicted from models both for appraisal and for ex-post evaluation purposes. Thus, the quality of measurements for input data for such models (typically traffic characteristics) determines the accuracy with which we may evaluate environmental performance of a charging scheme.