The Challenges of Conducting an Economic Appraisal of a Low Emissions Zone

The Challenges of Conducting an Economic Appraisal of a Low Emissions Zone


H Bowkett, L Harris, Peter Brett Associates, UK; R Leuillette, Reading Borough Council, UK


The paper looks at the modeling challenges for a low emissions zone, considers a wide range of potential benefits apart from air quality and discusses whether it is more appropriate to conduct a cost effectiveness appraisal.


The challenges of conducting an economic appraisal of a low emissions zone.

An increasing number of urban areas are facing air quality issues and are considering the introduction of a low emissions zone. In the UK this follows the example of the introduction of such a scheme in London which is considered to have resulted in the use of a cleaner commercial fleet than would otherwise have been the case. During the evaluation of a low emissions zone for Reading in the Thames Valley the study team became aware of many issues which made the economic appraisal a journey into uncharted territory. This paper aims to air the challenges faced, outline the issues discussed during the appraisal process and initiate discussion as to how the appraisal would be conducted in other European countries.

The first set of challenges arose during the modelling work to produce the forecasts of vehicle flows in and around the low emissions zone as a result of the introduction of the scheme. The Reading Transport Model is a variable demand model with income segmentation developed to test a road user charging scheme with associated public transport measures and highway network changes. The paper discusses the issues associated with first establishing the base year level of demand by commercial vehicles and then estimating the behavioural responses of commercial operators to a charge if their vehicle does not meet the set Euro specification. Some vehicles may re-route to avoid the low emissions zone area and the challenge is to ensure that these vehicles remain only on suitable routes. Others will upgrade their vehicles or fit abatement equipment while others will pay the charge, but modelling these responses posed challenges.

Secondly. the appraisal required consideration of all the benefits that would flow from the scheme. Only some of these could be valued using the DfT?s TUBA software, such as journey time and vehicle operating cost changes for commercial vehicles and other road users. A significant proportion of the benefits came from the air quality benefits from cleaner vehicles but the appraisal had to consider the rate at which the fleet would have become cleaner anyway without the low emissions zone. The paper also presents the valuation of other potential benefits considered such as accident reductions, road maintenance savings, noise issues and pedestrian ambience benefits.

Finally the paper discusses whether a traditional cost benefit approach is the most suitable tool for evaluating the introduction of a low emissions zone. One of the key motivations behind the introduction of the low emissions zone is the need to meet European air quality targets. Failure to reach these targets brings the significant risk of hefty fines so the paper considers whether it is more appropriate to conduct a cost effectiveness appraisal of the low emissions zone proposal.


Association for European Transport