DISSECTING PREFERENCE HETEROGENEITY IN CONSUMER STATED CHOICES

This paper investigates alternative methods to account for preference heterogeneity in choice experiments. The main interest lies in assessing the different results obtainable when investigating heterogeneity in various ways. This comparison can be performed on the basis of model performance and, more interesting, by evaluating willingness to pay measures. Preference heterogeneity analysis relates to the methods used to search for it. Socioeconomic variables can be interacted with attributes and/or alternative-specific constants. Similarly one can consider different subsets of data (strata variables) and estimate a multinomial logit model for each of them. Heterogeneity in preferences can be investigated by including it in the systematic component of utility or in the stochastic one. Mixed logit and latent class models are examples of the first approach. The former, in its random variable specification, allows for random taste variations assuming a specific distribution of the attribute coefficients over the population and permit to capture additional heterogeneity by consenting parameters to vary across individuals both randomly and systematically with observable variables. In other words it accounts for heterogeneity in the mean and in the variance of the distribution of the random parameters due to individual characteristics. Latent class models capture heterogeneity by considering a discrete underlying distribution of tastes. The small number of mass points are the unobserved segments or behavioral groups within which preferences are assumed homogeneous. The probability of membership in a latent class can be additionally made a function of individual characteristics. Alternatively, heterogeneity can be incorporated in terms of the random component of utility. The covariance heterogeneity model adopts the second approach representing a generalization of the nested logit model and can be used to explain heteroscedastic error structures in the data. It allows the inclusive value parameter to be a function of choice alternative attributes and/or individual characteristics. An alternative method refers to an extension of the multinomial logit model in which the integration of unobserved heterogeneity is performed through random error components distributed according to a tree. An interesting improvement in modeling preference heterogeneity is related to its simultaneous inclusion in both systematic and stochastic parts. A valid example is the inclusion of an error component part in a random coefficient specification of the mixed multinomial logit model. The empirical data used for comparing the various methods tested relates to departure airport choice in a multi-airport region. The area of study includes two regions in central Italy, Marche and Emilia-Romagna, and four airports: Ancona, Rimini, Forlì and Bologna. A fractional factorial experimental design was adopted to construct a four alternative choice set and five hypothetical choice exercises in each questionnaire. The selection of the potentially most important attributes and their relative levels was developed on the basis of previous research.heterogeneity, airport choice, stated preferences, discrete choice model.

Quality and Public Transport Service Contracts

Public authorities and transport operators are both involved in the provision of public transport services. There is a contrast between the social goals of the former and the private ones of the latter. Regulation plays an important role especially failing competition. Service contracts are the natural method to set bilateral After a brief description of the most important regulatory procedures, we focus our attention on the quality framework in service contracts. In recent years the inclusion of quality requirements in contracts is becoming common practice, especially when adopting price cap regulation. This paper suggests a criterion for service quality definition, measurement and integration in contracts for the production of socially valuable transport services. Using stated preferences methods and choice-based conjoint analysis to analyse customer preferences we estimate the passengers’ evaluation of different service features and calculate a service quality index. A case study demonstrates the procedure to follow for measuring service quality in local public transport.service quality, stated preferences, service contract.

Willingness to pay confidence interval estimation methods. Comparisons and extensions

This paper systematically compares methods to build confidence intervals for willingness to pay measures in a discrete choice context. It contributes to the literature by including methods developed in other research fields. Monte Carlo simulations are used to assess the performance of all the methods considered. The various scenarios evaluated reveal a certain skewness in the estimated willingness to pay distribution. This should be reflected in the confidence intervals. Results show that the commonly used Delta method, producing symmetric intervals around the point estimate, often fails to account for such a skewness. Both the Fieller method and the likelihood ratio test inversion method produce more realistic confidence intervals. Some bootstrap methods also perform reasonably well. Finally, empirical data are used to illustrate an application of the methods considere

Role-playing games as a mean to validate agent-based models: an application to stakeholder-driven urban freight transport policy-making

Abstract Agent-based models (ABMs) are widely used to replicate transport environments accounting for interaction among stakeholders. Validation of ABMs implies assessing the extent to which the model, from assumptions to results, is capable of approximating reality. To this end, different methods have been proposed, but yet no widely accepted procedure has emerged. This paper addresses this problem and suggests using a procedure based on role-playing games (RPGs). A first application is described with the intent of providing a preliminary contribution to validate an ABM trying to mimic stakeholders' interaction in a multi-level decision-making process in the context of urban freight transport policy-making. The aim is twofold: (1) understand if the structure of the model and the opinion dynamics envisioned are consistent with a real negotiation process, (2) verify if the results derived from the ABM effort are in line with those derived from a real-life experiment. Results of the first preliminary experiment show that the model seems capable of reproducing real-world processes and confirm that well-thought-out RPGs can contribute to validating ABMs

Role-playing games as a mean to validate agent-based models : an application to stakeholder-driven urban freight transport policymaking

Agent-based models (ABMs) are widely used to replicate transport environments accounting for interaction among stakeholders. Validation of ABMs implies assessing the extent to which the model, from assumptions to results, is capable of approximating reality. To this end, different methods have been proposed, but yet no widely accepted procedure has emerged. This paper addresses this problem and suggests using a procedure based on role-playing games (RPGs). A first application is described with the intent of providing a preliminary contribution to validate an ABM trying to mimic stakeholders’ interaction in a multi-level decisionmaking process in the context of urban freight transport policy-making. The aim is twofold: (1) understand if the structure of the model and the opinion dynamics envisioned are consistent with a real negotiation process, (2) verify if the results derived from the ABM effort are in line with those derived from a real-life experiment. Results of the first preliminary experiment show that the model seems capable of reproducing real-world processes and confirm that well-thought-out RPGs can contribute to validating ABMs. Keywords: city logistics, stakeholder engagement, participatory simulation, model validation, discrete choice modelspublishedVersio

Smart urban freight planning process: integrating desk, living lab and modelling approaches in decision-making

Abstract Purpose This paper proposes an innovative approach to decision-making processes for urban freight planning that could easily be transferred across cities while capable of jointly taking into account: (1) all the conceivable and updated urban freight transport (UFT) measures that should apply to the specific city culture, structure and evolution, (2) all the relevant stakeholders and successfully involve them from the beginning, (3) behavioural, technical, operational, organisational and financial issues. Methods The methodology is organised and deployed in three phases, following three different approaches, i.e.: a "desk approach" for data acquisition and knowledge-based policy rankings; a "living lab approach" to foster stakeholders' engagement in co-creating policies; a "modelling approach" to evaluate policies and find/define an optimised mix of shared applicable/effective policies. Results The three-phase methodology supports public authorities in: (a) increasing knowledge and understanding of the most innovative context-specific UFT policies; (b) integrating UFT policies in strategic urban planning via collaborative participation/governance processes; (c) developing an ex-ante behaviourally consistent, financially robust and technically compatible assessment of shared UFT policy mixes while providing appropriate instruments to facilitate policy adoption and deployment. Conclusions The proposed methodology contributes to the identification and development of effective UFT solutions. Bringing together knowledge acquisition, policy co-creation, behaviour change analysis within a single methodological approach, aimed at identifying an optimised policy package, is both new and needed

Sustainable urban freight transport adopting public transport-based crowdshipping for B2C deliveries

Abstract Cities crave innovative logistics solutions dealing with the requirements of the 'on demand economy'. The paper estimates the willingness to act as a crowdshipper (supply) and to buy a crowdshipping service (demand) to get goods delivered/picked-up in the last mile B2C e-commerce situation. Specifically, it innovates by considering an environmental-friendly crowdshipping based on the use of the mass transit network of the city where parcels customers/crowdshippers pick-up/drop-off goods in automated parcel lockers located either inside the transit stations or in the surroundings. This issue is very important since "standard" crowdshipping is usually not able to reduce congestion and polluting emissions due to the dedicated trips performed using private motorized vehicles. The paper rests on an extensive stated preference survey. The hypothetical scenarios used to acquire both demand (customers') and supply (crowdshippers') preferences make use of the most relevant attributes emerging from a preliminary investigation performed in the study context. The investigation is performed in the city of Rome and the metro is the transit system considered. The results are useful in understanding and quantifying the potential of this freight transport strategy for e-commerce in an urban context and in providing local policy makers with a good knowledge base for its future development

Sustainable crowdshipping using public transport: a case study evaluation in Rome

Abstract The paper analyses the willingness to act as a crowdshipper in the case of a last mile B2C e-commerce for pick up/delivery. Specifically, it focuses on crowdshipping services deployed using the public transport network and considering passengers as crowdshippers already moving for other reasons. In fact, this is the most environmental-friendly type of service one can develop given it avoids performing dedicated trips. The paper uses stated preference to identify the most important features associated with the choice of acting as a crowdshipper and discrete choice models to study the underlying behavior. The implementation case study refers to the city of Rome, Italy, and addresses its metro lines, thus understanding and quantifying the effects of this freight transport strategy for e-commerce in an urban context and providing local policy makers a good knowledge base for its future development

Digital twins : a critical discussion on their potential for supporting policy‐making and planning in urban logistics

Poor logistics efficiency, due to low load factors caused by high demand fragmentation, will have relevant negative consequences for cities in terms of pollution, congestion and overall city liveability. Policy-makers should equip themselves with appropriate tools to perform reliable, comprehensive and timely analyses of urban logistics scenarios, also considering upcoming (i) technological changes, (ii) business model evolutions and (iii) spatial-temporal changes these innovations will produce. This paper discusses the Digital Twin (DT) concept, illustrating the role it might play and clarifying how to properly conceive it with respect to urban freight transport policy-making and planning. The main message is that without a sound theory and knowledge with respect to the relationships linking contextual reality and choice/behaviour, it is not possible to make sense of what happens in the real world. Therefore, the joint use of behavioural and simulation models should characterise a DT within a Living Lab approach so to stimulate effective, well-informed and participated planning processes, but also to forecast both behaviour and reactions to structural changes and policy measures implementations. Keywords: digital twins, urban freight, living lab, behavioural models, policy, planningpublishedVersio