Costruzione di modelli di scelta discreta ibridi per misurare gli effetti delle strategie informative sulla scelta del modo di viaggio contestualmente agli aspetti latenti
Road traffic is now the main culprit of air pollution in urban areas, due to the emissions of the combustion products of fuels and their subsequent chemical transformation, as well as to the evaporation of unburned hydrocarbons. Transport accounts for 25% of CO2 emitted globally, and is also one of the few sectors where emissions have continued to grow, oil consumption between 1973 and 2010 increasing by 110% (IEA, 2011) and CO2 by 44 %. (IEA, 2009; Banister et al., 2012). Several actions and measures have been developed to try to mitigate the harmful emissions produced by the transport sector and in particular by road traffic. These largely concern vehicle technology, type of fuel, economic tools and institutional controls. Although powerful, these measures have not been proved to be sufficient to solve the problem (Schwanen et al., 2011). In recent years, research has consequently increasingly focused the attention on measures and policies that affect individuals’ behaviour and in particular what motivates their decisions. Providing information is the measure most used to promote behaviour change (Abrahamse and Matthies, 2012): "A person who has an attitude that suggests that it would be consistent for him or her to use the car less cannot bring about behaviour change if that person does not know how to change" (Ampt, 2003). It has been observed that measures that increase individual’s awareness can produce enduring changes, being the result of mindful decisions. This is at the basis of the concept of "Soft Measures", also referred to as "Voluntary Travel Behaviour Change" (VTBC) programmes (Ampt, 2003) or "Smarter Choices" (Cairns et al., 2004), i.e. programmes aimed at motivating the voluntary reduction of car use. VTBC programmes provide information typically on: a) the negative (mainly environmental) effects of current behaviour and b) how individuals can change their current behaviour to mitigate the negative effects. The types of information provided in these studies are mostly: travel time, mileage travelled, travel cost, time spent in non-working activities, CO2 emitted, calories burned. These studies assess the overall effectiveness of the programme, comparing the number of trips by car before and after the implementation of a soft measure. None of them have however examined which of the information provided actually leverages behaviour change. Understanding to what extent specific soft measures contribute to shape individuals’ preferences, is crucial for defining the best policy for fostering changes toward sustainable modes. Of the environmental effects, the information about the impact on the CO2 emitted is probably the most effective measure (and more understandable than other measures like for example PM10). The information on CO2 has often been used in VTBC programmes, and it is widely recognised that individuals are less likely to adopt environmentally friendly behaviour if this information is not provided. However research to date has not yet made it possible to disentangle its efficacy as a soft measure. As far as the information on health effects is concerned, the typical measure tested is the number of calories burned. This is a relatively easy measure to test, because it is easy to quantify and for the individuals easy to associate with the effects on their health. However, from the health literature it seems that rather than the calories burned, stress represents the real plague of modern society. Wener et al. (2010) found also that car commuters showed significantly higher levels of reported stress and more negative moods compared to train commuters. None of the studies however assess the effect of the information, i.e. to what extent being aware of the stress caused by driving has an impact on individuals’ decision to change transport mode. Therefore the objective of this thesis work is to contribute to the development of a programme for voluntary travel behaviour change, and to study the extent to which each single element of the soft measure contributes to the overall awareness. The study focuses in particular on the effect that information on pollution and individual stress has on the choice to shift from private car to Park and Ride (P&R). To try and disentangle the effect of these two components a Stated Preference (SP) experiment was built where the reduction of CO2 and the reduction of stress are attributes included in the experimental design. The ability to perceive, or to be conscious of something and to react to it (i.e. awareness) can differ from one person to another depending on their psychological stance toward environment and stress. Many studies have accounted for the effect of environmental attitude mainly in mode choice or type of fuel-vehicle choice. However, other latent effects other than attitude are relevant. In particular, in terms of environmental awareness and the information provided, personal norm measures a very interesting aspect as they evaluate the moral rule (and obligation) that lead individuals to act rightly or wrongly towards the environment. As for stress, the way individuals perceive stress caused by traffic and the way they perceive the information about stress are particularly relevant for the study. In particular the contribution of this thesis work is to define the methodology to use within a VTBC programme to account for all the above-mentioned aspects. The methodology used thus comprises a SP survey where soft measures information is directly included as attributes in the SP tasks presented to the individuals, a survey that follows the theory of planned behaviour (Ajzen, 1991) to specifically measure psychological aspects that could influence the impact of the information provided and/or mode choice. The use of information attributes in the SP is not common and deserves further consideration. The major challenges in including the information about CO2 and stress as attributes concern how they should be presented to respondents in order to be clearly understood. We devoted special attention to studying the best way to present the soft measures in the SP survey. In particular we tested the following aspects: 1) whether to use images alone, only text or both; 2) the type of information that should be included in the text. The major difficulty lies in explaining to people what the information provided means; 3) the type of context to be included in the images; 4) whether to use abstract or real images i.e. cartoons or real people. Lastly, to analyse the data collected, several hybrid choice models (HCM) have been estimated so as to assess the effect of awareness and psychological aspects in the discrete choice between car and P&R. The results show that 1) the utility to P&R increases with the level of awareness attained thanks to the information about the light rail alternative, 2) the more individuals consider receiving information about stress useful, the more they tend to behave sustainably, choosing P&R, 3) those aspects associated with stress would appear to have a greater influence on travel choice than environmental aspects.The thesis work highlighted the importance of being able to completely evaluate the behavioural process so as to enhance the effectiveness of VTBC programme implementation. An incorrect evaluation of the definition and implementation of measures, as well as of all those attributes influencing travel behaviour, could impair the effectiveness of those measures, and in terms of modelling, result in inaccuracy in travel demand forecasting.
comportamento di viaggio, discrete choice models, latent variables, misure informative, modelli di scelta discreta, preferenze di chiamate, soft measures, stated preference, stress, travel behaviour, variabili latenti, Settore ICAR/05 - Trasporti
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