The paper describes a series of experiments to assess behavioural responses to a number of possible charging regimes. The data sources have included: (1) A series of questionnaires seeking attitudes, perceptions and expected responses; (2) A specially adapted version of the VLADIMIR route-choice simulator used to explore route choice responses; (3) A full scale driving simulator to investigate the consequences of time-based charges on road safety; and (4) Field trials using specially equipped vehicles to explore the influence of real constraints on behavioural response to charges. A particular feature of the experimental work has been the use of real money to engender realistic responses. The results suggest that, if charges are based on time spent in the network, even very low charges would induce drivers to drive less carefully. It was found that, where available, the dominant responses to charging are route switching and change in departure time; use of alternative modes is very much a minority response. Charges appear to have little impact on the choice of routes within a charge area but can have a very important effect at the boundaries. It is noted that, in practice, personal circumstances frequently constrain peoples' ability to respond to the charges as they might wish. Respondents have expressed particular dislike for charging regimes where the exact charge is not known prior to the journey and it appears that, other things being equal, they will incur a fixed charge rather than a variable one with the same mean value. It appears that the response to road charging may be modelled using a hierarchical logit model to predict the nature of the response and an appropriately disaggregate assignment model to predict the route choices and hence the network effects.
Abstract