Urban Road User Charging Online Knowledge Base
What Is The Importance Of The Theme?
In a scheme which is as complex as road pricing, it will be unlikely, as discussed in Chapter 11, that the public will readily accept all aspects of the scheme once it has been implemented. At the very least, therefore, evaluation will provide a means of obtaining the evidence with which to answer the scheme’s continuing critics and to increase public acceptance. In practice, it is probable that some aspects of the scheme will not work as well as planned. In such cases, evaluation provides the evidence that improvements are needed, and the basis for enhancing the scheme’s effectiveness. More generally, with a policy as novel as road pricing, evaluation provides empirical evidence which will help other cities decide whether they would benefit from a similar policy. The series of annual evaluations of the London Congestion Charging Scheme (TfL, 2003-2008) and the evaluation of the Stockholm scheme (Stockholmsförsöket, 2006a), are already being used internationally as input to other cities’ policy decisions.
Finally, as discussed in Chapter 6, comparison between evaluation of the actual outcome, and appraisal of the predicted outcome, will help to assess whether the process of prediction was effective, or whether enhancements are needed to the predictive models used.
Thus evaluation can be used to answer four types of question:
Did the scheme work effectively in meeting our objectives?
Are there aspects of the scheme which merit improvement?
Were the predictions accurate, or are improvements needed in the prediction process?
Is this scheme (in another city) something which I should be considering for my city?
While the first three of these questions can focus solely on the objectives and constraints of the city which implemented the scheme, evaluation to satisfy the fourth question should ideally cover all the objectives which other cities might have. Thus ideally, evaluation should also consider the objectives of interest to other cities, so that the results are potentially able to be transferred to other locations, as discussed in Chapter 12. The full set of objectives has been listed in Chapter 2.
Evaluation was not identified separately in the UNAQ. In practice, as noted above, it is likely to be critical in answering the continuing critics of a scheme. In the longer term it is extremely important, to politicians, professionals and researchers, in order to further knowledge about the predicted and observed impacts of road pricing schemes. However, in the aftermath of implementation, there may be a danger that it will not be given the priority it deserves by local decision-makers. The history of transport planning innovations suggests a general lack of “after” studies, probably because by that stage the major political decisions have been taken and thus such studies have not been seen as having a critical role to play in future policy. In the case of road pricing, the level of academic, political, media and public interest in the relatively small number of implementations to date has encouraged the collection and dissemination of a considerable volume of “after” data. However, there remains a challenge to ensure that evaluation continues to further our understanding of the impacts of road pricing (such as through common indicators that can be compared across different schemes). The international community should therefore encourage all cities to carry out comprehensive evaluations of the schemes which they implement.
What should we evaluate and monitor?
As noted above, evaluation should ideally cover performance against all of the objectives listed in Chapter 2. The information on performance against each objective can be kept separate, or aggregated, potentially using weights or money values, using any of the methods outlined in Chapter 11. Particular care will be needed with evaluation against the equity objective, where evidence on effects on different impact groups may need to be kept separate.
Monitoring can usefully extend more widely to cover the behavioural changes and resulting traffic effects (Chapter 7) which explain performance against objectives, and may be of value in their own right in helping the public to understand what has happened.
How does evaluation relate to prediction and appraisal?
In general, the evaluation process does not need prediction, since impacts have occurred and can in most cases be measured. However a comparison between appraisal and evaluation can indicate how well the prediction process has worked. (see for example, Eliassson (2008)). Effective evaluation is thus central to enhancing the prediction process.
No information on this theme is currently available from the case studies