Complex Congestion Charging ? an Assessment of Motorists? Comprehension and the Impact on Their Driving Behaviour

Complex Congestion Charging ? an Assessment of Motorists? Comprehension and the Impact on Their Driving Behaviour


P Bonsall, J Shires, ITS, University of Leeds, UK; H Link, A Becker, DIW (German Institute for Economic Research), DE


Results of questionnaire surveys in the UK and Germany exploring drivers' ability to understand and respond to differentiated road charges.


This paper is based on work within GRACE (a European Commission project) and extends research by ITS Leeds on behalf of the UK Department of Transport. GRACE aims to facilitate implementation of pricing and taxation schemes reflecting the full costs of infrastructure use. This paper is based upon a GRACE Work Package which is examining the optimal degree of complexity in transport charges and focusses on motorists? ability to comprehend and respond to such charges.

A questionnaire was designed to gain an insight into how people would deal with complex congestion pricing regimes and the impacts that such schemes would have on their driving behaviour. More specifically, the questionnaires were designed (1) to quantify peoples? ability to estimate their current motoring costs and to comprehend complex congestion pricing regimes; (2) to identify the factors influencing people?s ability to estimate costs and charges; and (4) to measure the potential impact of complex congestion charging regimes on driver behaviour.

Similar questionnaires were used in each of two areas (Newcastle-upon-Tyne in UK and Cologne in Germany). The questionnaire comprised two phases; a face-to-face screening phase - following which eligible respondents were asked to study documentation describing a (hypothetical) road charging scheme in their city, and a CATI (computer assisted telephone interview) phase which probed their comprehension of, and response to, that scheme.

The first phase interview established the characteristics of the respondents, their regular journeys and the alternative modes they could use, their sensitivity to cost costs, and their willingness to take part in a further telephone interview. The data obtained from phase one was used to allocate an appropriate congestion charging schemes to those respondents. Three variant schemes had been prepared for each city; they varied in terms of the complexity of the charges levied (varying by time periods, road type etc.) and the areas they covered.

The surveys were conducted in Autumn 2006 and resulted in 400 fully completed returns (with the UK-Germany split being approximately 50-50).

Although all the key questions were essentially the same in both versions of the questionnaire, some differences were inevitable due to differences in language and culture and due to the fact that the hypothesised charging schemes in Cologne inevitably differed from those in Newcastle. Great care must thus be taken to allow for differences in the questionnaire context when interpreting the questionnaire results.

Initial analysis of the data provides some interesting insight into people?s perception of and response to costs and charges. One particularly interesting finding, which was particularly marked in the UK, is that a substantial minority (UK 30%, Germany 18%) said that they ?rarely? put much effort into working out the best deal for their utility services. Another, which was again most marked in the UK, is that respondents claimed much higher levels of ability to estimate the (hypothesised) congestion charge for their most regular journey than they had claimed to estimate the current costs of that journey (84% of UK respondents claimed that they could estimate the congestion charge cost to within 50 pence whereas only 47 % of them claimed similar precision for their estimate of the current of that journey ? the equivalent German results being 98% and 81% respectively for a precision of 1 Euro).

Respondents gave various reasons for their difficulty in estimating the congestion charge. The main reasons cited were: the complexity of the calculation (Germany 33%, UK 17%), uncertainty about the precise length of the route (UK 31%, Germany 12%), the difficulty knowing what time they would be travelling (Germany 20%, UK 12%), and uncertainty about precisely where the charges would apply (UK 12%, Germany 14%).

A substantial minority (UK 44%, Germany 22%) said that they would not start to think seriously about changing their travel arrangements unless the monthly charge exceeded £25 and only a small minority (UK 10%, Germany 9%) thought that they could reduce the charge payable by switching to an alternative route.

Our analysis thus far is suggesting that the pricing signals contained in complex, or highly differentiated, congestion charges are unlikely to affect the behaviour of many motorists. This is partly because they fail to perceive or understand the price signal, partly because they think they have no option but to pay up and partly because they would not bother to think seriously about it.

Further analysis, to be reported in the full paper, will pursue these themes and seek to develop and calibrate a series of driver behaviour models.


Association for European Transport