Inter-temporal Variations in Values of Time in Great Britain
N Tapley, M Wardman, ITS, University of Leeds, UK; H Gunn, HGA, UK; G Hyman, Department for Transport, UK
A reduced-scale repeat of the 1994 UK national value of time study has recently been undertaken in the West Midlands region of England by the Department for Transport (DfT).
National value of time (VOT) studies provide us with a valuable source of information regarding the attitudes and preferences of travellers. Countries such as Britain, The Netherlands, Sweden, Switzerland, Norway and Denmark have all conducted national studies and have used their results in the appraisal of both major and minor transport-related projects.
While the importance of these studies is clear, less emphasis has been placed on researching how respondents? attitudes to and valuations of transport-related attributes change over time. This is a crucial area of investigation as the costly nature of these national studies means that there will typically be some years between studies, if they are repeated at all. Thus, we must be sure that the results of these studies are valid over a number of years and therefore need to know if and why attribute valuations change. This study is an attempt to address this issue.
During the course of the current study of M6 Toll (M6T) users the opportunity was taken to conduct a reduced-scale repeat of the 1994 UK study. Questionnaires were distributed to motorists at seven motorway service areas (MSA) in the West Midlands region. The MSA sites were chosen to maximise the possibility of getting in-scope (i.e. those who could use the M6T road) respondents for the main study. Those who were not in scope were handed a version of the repeat study questionnaire. The questionnaires used in the repeat were nearly identical to those used in the original 1994 study. The main difference was that income bands and cost levels in the stated preference (SP) experiments were uplifted in line with inflation.
Each questionnaire asked the respondent to provide information relating to their current trip purpose, trip characteristics and socioeconomic data. In addition they were asked to complete three SP experiments.
Two of these SP experiments were given to all respondents. The first involved a choice between two unlabelled routes defined by journey time and travel cost. The second involved a choice between a tolled and untolled route, this time defined by journey time and travel/toll cost. In addition respondents were given a third SP experiment, which differed according to the length of the journey they were undertaking on the motorway. For some individuals, the SP experiment involved a route choice that included road characteristics (coach/lorry access, number of lanes, hard shoulder). For others the third SP experiment involved a route choice based on departure time. Finally, others were given an SP experiment that included a ?chance of delay? attribute.
The questionnaire distribution was carried out over four weeks in November 2006. Individuals were handed one of these questionnaires and asked to complete them once they had completed their current journey. They were provided with freepost envelopes with which to send the completed questionnaires back.
In total, 1399 questionnaires were returned. This compares with 1129 motorway questionnaires returned in the original 1994 study (out of a total of 4322 returned).
The questionnaires have recently been coded up and the analysis is currently underway.
The original 1994 study looked at variations in the value of time due to factors such as trip purpose/user type, journey length/characteristics and gains and losses on the current situation. The first phase of this analysis will therefore use the original model specifications to replicate the original analysis.
After this phase has been completed, we will compare the results with the original study. For example, we wish to compare the socioeconomic and journey characteristics of respondents from both studies to determine if any significant changes have occurred in the last twelve years.
As we have access to the 1994 choice data we then intend to estimate a joint model to investigate whether the relative valuations of any attributes have changed over time. For example, we wish to look at whether the relative value of toll charges to other travel costs has changed. It may be that as toll charges become more common individuals become less averse to paying them. Similarly, factors such as congested travel time and the possibility of delays may be valued more negatively as they become more common on our roads.
Finally, we will compare the results of the repeat study with the main study to determine if additional insights can be gained into the value of time. For example, respondents to this questionnaire were, by definition, non M6 Toll users (or potential users). We will investigate whether there is a significant difference in values of time between these respondents and those from the main study.
Association for European Transport