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Investigating the potential of the combination of random utility models (CoRUM) for discrete choice modelling and travel demand analysis
Full text linkPeople make choices every day. Many choices have a strong impact on the quality or their life.Each day a person wakes up and chooses which action he wants to do before, what to have for breakfast, what to wear, what time to go outside, how to manage his/her day by virtue of the budget and time constraints, which place to move to and how, which activity to do, which one to do before or after and so forth. There are choices that are not made every day, but they have a strong impact on the decision maker’s well-being. In fact, sooner or later, a person will decide his household location, whether to own a car, the typology and the vehicle model, whether to own a pet, which breed or size, how many children to have, in which school register them and much more.
Some of the above-mentioned choice examples involve mobility. Thus, it is easy to recognize why these kind of choices form the basis for the planning and policy actions in the transport field. What is called, at aggregate level, congestion or traffic, represents the sum of individual choices that everyone makes at different levels: do I move? What time do I move? Where I want to go? Which transport mode do I want to use? What itinerary do I travel?
This kind of choices, that can be termed transport choices, relating the so-called travel behaviour, are characterized by a significant modelling complexity. The random utility theory represents the most widely used paradigm in modelling the behaviour of people who make choices.
This thesis investigates the potential of the combination of random utility models (CoRUM; Papola, 2016) for travel demand analysis and discrete choice modelling in general. In the current work, several theoretical advances and some specific transport-field applications are carried out. The CoRUM framework, in fact, is very general and allows for handling several discrete choice modelling crucial issues.
The thesis is structured as follows:
Chapter 2 reviews the state of the art on random utility theory and its application to route choice. In particular, the Section 2.1 provides the basic setup for the description of RUMs; Section 2.2 reviews the random utility models available in the literature, with reference to the two main problems of the error structure (inter-correlations and heteroskedasticity problems) and the inter/intra-respondent taste variation; Section 2.3 briefly summarizes the main applications of the random utility theory to the route choice problem; Section 2.4 describes the main assumptions of the Combination of random utility models (CoRUM) as a general framework for modelling discrete choices, with particular reference to travel choices. Chapter 3 investigates more general specifications of the CoRUM than those previously analysed, allowing accommodating also the taste heterogeneity and the heteroscedasticity, in particular by combining mixtures of RUMs. To this end, the chapter proposes a theoretical generalization of the CoRUM framework and a real-world application on data collected on a stated survey of 1688 observations of 211 respondents. Chapter 4 represents an estimation exercise with applications on future scenarios on the main closed form random utility models, on synthetic datasets with variable sample sizes and complex underlying correlation scenarios. Such correlation scenarios, on the other hand, can be representative of typical mode choice or route choice contexts. The aim of this chapter is investigating the potential of the CoNL (and the other models) in terms of forecasting, and comparing it with the models goodness of fit performances. Chapter 5 proposes a new route choice model obtained under the CoRUM framework. It describes an algorithm to generate a CoNL specification, allowing detecting a set and a composition for the components of the model, and a way to compute all the structural model parameters, whatever the network.
Chapter 6 is currently an original contribution of this thesis and describes several advance compared to the published work in Chapter 5. In particular, an implicit enumeration algorithm theoretically consistent with the CoRUM route choice model,is proposed and tested on toy networks; an in-depth analysis of the complex route choice models is carried out on their ability to reproduce complex correlation scenarios, drawing important conclusions, both theoretical and applicative, on the novel CoNL route choice model, proposed in Chapter 5, and on the existent Link Nested Logit model; some practical advance on the original route choice model is proposed and tested both on toy networks and on a real network (Region Campania network). The goodness of fit of the CoNL route choice has been analysed and compared with the one of the other route choice models, using real observations collected by means of GPS detection of about 200 trajectories. Chapter 7 reports a summary of the conclusions reached in the whole thesis and proposes several ideas for future research steps
Mixing distributions of tastes with a Combination of Nested Logit (CoNL) kernel: Formulation and performance analysis
No full textThis paper explores the potential of a special instance of the Combination of Random Utility Models (CoRUM; Papola, 2016), termed Combination of Nested Logit (CoNL), as kernel model in conjunction with several types of mixing distributions of tastes (parametric, nonparametric, semiparametric). Various model formulations are illustrated with their mathematical properties, and several alternative kernel models are identified for comparison. An estimation exercise is presented on a real mode choice dataset from a stated preference survey on the intercity corridor between Naples and Milan in Italy. Results, in terms of both in-sample and out-of-sample goodness-of-fit on a 10-fold cross-validation show that models with the proposed CoNL kernel outperform contrasted models
Measuring the reliability of methods and algorithms for route choice set generation: Empirical evidence from a survey in the Naples metropolitan area
Full text linkBackground:
Route choice set definition is a very sensitive phase of the route choice simulation. Several heuristics, generally based on shortest path algorithm
repetition, give as output choice sets that are very large, lading to questions about their behavioural consistency.
Objective:
This paper proposes a comparison of the main route choice set generation methods, contrasting the results of the commonly implemented heuristics
with the revealed choice sets of a sample of employees and students moving within the Metropolitan Area of Naples.
Methods:
We described the data collection process and provided a statistical analysis of the sample data. In addition, since coverage measures and
performance indicators, usually applied in the literature, do not take into account any possible biases related to the generated choice set cardinality.
The current work proposes an analysis of the coverage of routes that are generated by the heuristics towards the revealed routes.
Results:
We observed that when the heuristics did not provide overlapped routes, although giving higher network coverage, they introduced a higher
number of links not belonging to any observed route. In general, this may cause significant network loading errors. Therefore, the quality of a
method for choice set generation should be measured as a function of the trade-off amongst network coverage and network loading bias due to
excessive cardinality of the generated choice-sets.
Conclusion:
We found the randomization method, which is also less computational demanding, provided the best trade-off amongst network coverage and
network loading bia
Evaluating the choice behaviour of high-speed rail passengers in Italy: A latent class structure with alternative kernel models to the Multinomial Logit
No full textThis paper analyzes the choice behavior of the high-speed rail Italian passengers, with a random utility latent class structure for modelling travelers' tastes. Latent class structures are widely used for addressing inter/intra-respondent taste variation in transport field. The simple Multinomial Logit (MNL) is commonly used as a kernel model (in the sense it will be clarified in the paper) into such latent class structures. The resulting random utility model (RUM) is well known in the literature as latent class Multinomial Logit (LC-MNL). In this study, we propose to test kernel models with different inherent distributional assumptions for random residuals of the utilities than that of the simple Multinomial Logit (MNL), namely the Gumbel distribution assumption (Extreme Value type I). Such different kernel RUMs are obtained by assuming random residuals of the utilities distributed as: Weibull (i.e. Extreme Value-type III), Exponential, Rayleigh, Pareto and q-Gumbel. Results on an estimation exercise, based on a dataset coming from a stated preference (SP) survey, show that some of these assumptions allow the resulting LC-RUM to outperform the well-known LC-MNL in terms of goodness of fit (GOF
Ecodriving in high frequency rail services
No full textIn recent years an increasing attention has been paid to energy efficiency in rail transportation. The problem of energy saving involves timetable and speed profile optimization and has been widely addressed in the literature. This paper deals with the trajectory optimization within high frequency rail systems, where the service is based on a scheduled headway rather than by a timetable. In this context, the reserve time holds for the whole line and the paper provides an assessment of its optimal split amongst the sections, taking into account the possible delays. This aspect enables the evaluation of the effects of delays on the trajectories optimization effectiveness
Towards a bottom-up estimation of a standard unit operating cost for bus operators: Methodology and policy implications in Italy
No full textThe paper proposes a bottom-up model for the calculation of unit operating costs of bus operators, with the aim of informing a more realistic calculation of standard costs in public transport. Standard costs are a key input for a more effective allocation of public resources to bus operators in Italy and allow for setting a virtuous circle towards more efficient public transport systems. Based on easy-to-collect data, an explicit dependence of some cost components upon relevant context/service variables faced by bus operators is introduced, ameliorating existing methods currently adopted. This enables bus operators to identify directions to improve their performance and public bodies to resort to more effective standard cost estimations. The viability of the proposed approach is showcased in the real case of Azienda Napoletana Mobilità, the biggest bus operator in the city of Naples (Italy), with examples of company-oriented and policy-oriented implications
Improving O-D flows updating through aggregation of O-D pairs: Methodological formulation and performance analysis of a heuristic algorithm
No full textPerformance of origin-destination (o-d) flows updating using link counts is highly influenced by the unbalance between the information provided by link counts and the number of o-d flows to update. In this respect, the paper proposes an approach to update o-d flows, based on their aggregation through a sequential algorithm, whose inputs are a prior o-d flows estimate, a set of counted links, and a prior estimate of the assignment matrix. The approach aggregates sequentially suitable pairs of o-d flows with a stepwise selection based on two criteria, namely coverage and proximity. Resulting aggregated o-d flows are then updated by means of a classical Generalized Least Squares (GLS) estimator. Finally, resulting updated o-d flows are disaggregated back to the original granularity using o-d flow proportions coming from the prior o-d flows estimate, thus introducing a bias. Notwithstanding, experimental results on a real-size network show the proposed approach to improve significantly o-d flows updating. Rules-of-thumb for the application of the proposed approach are also discussed, with operational and interesting implications for researchers and practitioners
Walkability, accessibility to metro stations and retail location choice: Some evidence from the case study of Naples
Full text linkRetail location choice and transportation systems are strictly dependent on each other. If, from one hand, the former has clear effects on the latter (being one of the determinants of travel demand), it is interesting to assess also the reverse impact. In this respect, notwithstanding the impact of accessibility to metro stations has been investigated in previous literature, few studies have highlighted the effect of active travel modes on retail location choice, so as no previous study has analysed this impact at a disaggregate level through a Stated Preference (SP) survey. This paper focuses on the choice behaviour of single retailers / managers of three densest urban retail districts in the city of Naples (in the South of Italy). The work analysis the impact of walkability and accessibility to metro stations on retail / businesses location choice. A SP survey and the estimation of several random utility models (RUM) have been carried out, with the aim of evaluating the distribution of retailers\u27 Willingness To Pay (WTP). Results show that retailers are more willing to pay for locating their activities close to pedestrian zones rather than metro stations and provides other insights on the effect of socio-demographic variables
Accessibility analysis in spatial planning: A case of special economic zones (SEZs) in Campania, Southern Italy
Full text linkThe strategic role of Special Economic Zones (SEZ) at the Italian level has also been underlined by the Italian National Recovery and Resilience Plan, which has provided an important economic endowment to relaunch the national economy, in general, and the Campania region territorial economy, in particular. Literature and best practices clearly show that many factors determine the success of a SEZ, with transport accessibility being one of the key factors. This study performs a transport accessibility analysis both at national and first/last-leg levels, by comparing the accessibility of the Campania SEZ areas, the other SEZ areas in Italy and all the other Italian local labour systems. The study focuses on the Campania region, as it represents the first Italian pilot project of spatial planning through the establishment of SEZs. The Campania region exhibits, on average, good transport accessibility both at a national level (considering the multi-modal freight Italian transport network) and at a first/last-leg level (considering relevant nodes of the network, such as tollbooths, freight stations, ports, interports and airports). Also, the impact of SEZ implementation on land use planning has been discussed, to provide a useful tool for stakeholders that are interested in revitalizing the area, at different levels: i) land use policymakers, to plan interventions/planning concerning infrastructures and spatial planning; ii) national policymakers, to establish SEZs in other geographical areas; iii) investors, to assess the convenience of investments in this geographical area
Ro-Ro/Ro-Pax maritime transport in Italy: A policy-oriented market analysis
No full textThis paper proposes an in-depth analysis of Ro-Ro/Ro-Pax services in the Western Mediterranean, with a focus on Italy. Following an already consolidated research track, a database of Ro-Ro/Ro-Pax services has been built and analysed, enabling policy insights on port connectivity, market positioning of shipping companies across ports and routes, and congestion of Ro-Ro/Ro-Pax port terminals. Furthermore, an adaptation of the well-known GLS-based procedure that updates/estimates o-d flows from traffic measurements has been proposed, to estimate Ro-Ro/Ro-Pax freight flows between ports in a study area, given the total inbound/outbound port throughput and the total weekly capacity of port-to-port services. Application to both a laboratory experiment and to a real case study yielded very effective results. Overall, the presented analyses update earlier contributions in the literature and set the basis for an observatory on Ro-Ro/Ro-Pax services that might be regularly brought up to date and applied also to other countries
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