Urban Road User Charging Online Knowledge Base
What Are The Research Gaps?
Based on the literature study, we conclude that the primary target areas for future research on this topic should be the following:
Firstly, it is unclear as to the effect that congestion “in itself” (driving characteristics) has on emissions. There seems to be a general assumption among the public as well as “congestion-oriented” traffic researchers, that reducing congestion (less stop-and-go, more “smooth” driving) is important to improve urban air quality. The limited research in this area seems less conclusive, and does anyway point clearly to the fact that reducing volumes is much more important than reducing congestion per se.
Secondly, there seems to be room for trans-disciplinary research centred on consensus-building for charging based on combinations of congestion and environment arguments. To what extent do these arguments appeal to the same segment of voters? To what extent are those arguments automatically conflicting through basic antipathy (so that e.g. those that want to support an environmental policy, would be against if it turned out to reduce congestion)?
Finally, there is a need to combine analyses of short term adaptation to charging, and long term decisions with respect to car ownership. Only on the basis of such a combined analysis would it be possible to identify reasonably “optimal” combined strategies with respect to charging exemptions (or reductions) for green cars, other types of economic incentives for car fleet transition, and charging effectiveness.