Project: Psychological Factors Affecting Transport Mode Choice A64
Reference: STP 14/5/6
Last update: 31/12/2009 11:45:00
The objectives are to:
Identify relevant attitudinal factors upon which transport decisions are made;
Develop a measurement tool for quantifying and weighting the attitudinal factors in terms of their relative impact on transport decisions;
Identify variation in the factors that impact on different population sub-group's transport decisions;
Produce an empirically standardised tool and related normative database for the ongoing measurement of attitudes and the evaluation of policy impact at local and national levels.
The success of campaigns and policies directed toward reducing private car use is, for the most part, dependent upon understanding the psychological factors that influence an individual's travel mode decisions. In general, however, interventions to reduce car use have been based on informal conceptualisations, designed without elicitation research, and directed primarily at providing information about the negative consequences of car use. This information is usually not sufficient to change behaviour. In fact, whether people choose to drive or take public transport has been found to be only weakly related to their knowledge about the environmentally damaging effects of extensive private car use. Intervention strategies based on empirically validated theories are more promising, though in relation to choice of travel mode, there is a lack of research that utilise such approaches. The theory of planned behaviour has provided one of the most influential contributions to the field of attitude measurement and the prediction of behaviour. The application of this theory to travel choice will provide an empirically grounded model to help understand the reasons why drivers currently prefer to use their car rather than using public transport.
Mulberry Research and Consulting Ltd
Magnolia House, 102 Hoole Road, Chester, Cheshire, CH2 3NU
Cost to the Department: £52,768.00
Actual start date: 01 September 2001
Actual completion date: 04 August 2004
Psychological Factors Affecting Transport Mode Choice: Identification and Measurement Tool Development
Author: Mulberry Research & Consulting Ltd
Publication date: 29/10/2003
Summary of results
- Mulberry Research & Consulting Ltd. was commissioned by the DfT to investigate the psychological factors associated with public transport and private car use. The research identified: the main attitudinal factors that predicted modal choice; the most salient beliefs that underpinned these decisions; and that there were demographic differences in these preferences. The research programme had three phases. The first comprised a review of the relevant literature. Interviews were also held at this phase to elicit the most salient beliefs underlying transport mode decisions. This qualitative approach informed the second, quantitative, phase of the research, which involved the development and validation of a transport mode instrument. In the final phase a large-scale survey of transport mode choice was undertaken.
A review of the research literature between 1967 and 2001 revealed a large number of publications concerned with psychological factors and transport. However, only seven were explicitly concerned with transport mode choice. Contrasting this knowledge gap, the review indicated that during the same period, a great deal of systematic research had been conducted that examined the psychological correlates of behaviour. One model - the theory of planned behaviour (Ajzen, 1991) - stood out as influencing this field. The theory assumes that most actions can be viewed as deliberative, planned behaviours. By this, it is meant that individuals make an active choice such as using a particular transport mode, on the basis of a systematic analysis of the alternatives. According to the model, people ultimately make a decision, known as a behavioural intention based on three factors. These are: attitude to the behaviour (a person's positive or negative evaluation of performing a behaviour); subjective norm (perceived social pressure to perform the behaviour); and perceived behavioural control (perceptions of whether it is feasible to perform the behaviour). In relation to transport, it would be expected that people are more likely to adopt a particular mode if they have a favourable evaluation of it, perceive social pressure to use it and believe it is a viable option. The theory of planned behaviour also explains how individuals form their attitude, subjective norm, and perceived behavioural control. Each is based on a person's salient beliefs. These are behavioural beliefs (the costs and benefits of performing the behaviour), normative beliefs (specific individuals and groups who would approve of one performing the behaviour) and control beliefs (specific factors that would inhibit or facilitate performance of the behaviour) for attitude, subjective norm, and perceived behavioural control respectively.
Although the theory of planned behaviour claims that behaviour is determined solely by attitude, subjective norm, and perceived behavioural control, research has shown that they are rarely sufficient to provide a complete account of the decision-making process. As a result, four additional variables were also included. These were environmental concern, moral norm (internalised notions of whether it is right/wrong to perform the behaviour), behavioural norm (perceptions of others' behaviour) and habit (the tendency to use a particular transport mode to travel to a variety of destinations).
Semi-structured interviews were held on an individual basis with 80 members of the public. The interviews involved asking participants to list: the advantages and disadvantages of driving or using public transport to commute to work; groups and individuals that approved and disapproved of them using the transport modes; and the factors that would prevent them or increase the likelihood of them using either transport mode. The data were content analysed to identify the most salient beliefs underlying travel mode choice. These beliefs could be grouped into three categories: beliefs concerning the positive and negative consequences of using each transport mode; beliefs concerning individuals and groups who would approve or disapprove of each mode; and beliefs concerning factors that would increase or decrease the likelihood of using each mode.
The results indicated that participants considered the advantages of using their car were: reduced journey time; convenience; flexibility and freedom; and reliability. Car use was also associated with a number of disadvantages. These were: expense; congestion; environmental effects; and parking difficulties. The advantages of using public transport were that: it protects the environment; eases congestion; alleviates parking problems; and is more cost effective than using a car. The perceived disadvantages were that: it is unreliable; takes too long; is unhygienic; overcrowded; and inconvenient.
The respondents reported that they would be more inclined to use public transport if: it was more reliable; cheaper; more frequent; and quicker. In contrast, they claimed they would continue to use their cars to commute if: the overall cost of car use reduced; if the price of public transport increased; and if they were under time pressures.
The most important individuals or groups with respect to influencing transport mode choice were: employer; pro-environmental groups; petrol companies; car manufacturers; the Government; and cyclists. The beliefs elicited at this stage were used as the basis for the closed-format questionnaire, which was piloted in the second phase of research.
Development and validation of the pilot tool
Following extensive pilot work, a closed-format questionnaire was designed to assess the most important factors underlying decisions to commute. The questionnaire was distributed to 200 members of the public and the resulting data were analysed to establish the psychometric properties of the instrument.
The analysis revealed that not all of the beliefs deemed salient in the first phase of the research impacted directly on modal choice. As a result, it was possible to develop a shorter questionnaire, containing only the most important factors underlying transport mode choice for the large-scale survey. The most important findings to emerge from this phase of the research were that transport mode decisions could be predicted by attitudinally-based factors. In particular, intentions to drive to work and commute using public transport were predicted from a person's attitude, perceptions of social pressure, and perceptions of behavioural control. It was also the case that a person's habitual choice of transport also influenced commuting intentions.
Transport decisions survey
Trained interviewers collected data from 829 respondents who were stratified according to gender, age and location (urban/rural areas in the north and south of England). Data were analysed to identify why respondents used public transport and/or drove to work. The analysis revealed that five factors determined modal choice. For both behaviours, decisions were relatively automated in the sense that habit was the most influential predictor of transport mode decisions. Nevertheless, four psychological constructs directly informed decisions. These were: attitude; subjective norm; behavioural norm; and perceived behavioural control. Participants were therefore more likely to use a particular mode if they had a favourable evaluation of it, perceived social pressure to use it (in terms of the approval and behaviour of significant others) and believed its use was feasible. Two additional constructs - moral norm and environmental concern - impacted indirectly on intentions through the development of travel habits.
Further analysis was undertaken to pinpoint the specific beliefs that underlined modal preferences, and those that discriminated between people who intended to use each mode from those who did not. This established the beliefs that would have to be changed in promotional campaigns if modal shift is to occur.
Interestingly and importantly, the psychological model of modal choice was sufficient to mediate the effects of demographic variables (age, gender and marital status) and other background variables (annual mileage and distance from nearest transport stop). This indicates that it is a person's psychological disposition that is primarily responsible for transport mode choice. Nevertheless, systematic differences existed between different subgroups of the population. In particular, the predictive ability of the factors varied according to the particular behaviour (private car use and public transport), age group, and to a lesser extent, gender.
The findings of the research programme provide a significant advance on what is currently available. An empirically grounded model was developed which explained why drivers currently prefer to use their car rather than using public transport. Understandably, many of the beliefs corresponded to 'common-sense' or intuitive notions over what would promote public transport use that have been identified in previous research. However, they were empirically validated and their differential importance was established within a theoretical framework.