Browsing by Author "Ortuzar, Juan de Dios"

Now showing 1 - 9 of 9
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    A discrete choice model incorporating thresholds for perception in attribute values
    (PERGAMON-ELSEVIER SCIENCE LTD, 2006) Cantillo, Victor; Heydecker, Benjamin; Ortuzar, Juan de Dios
    In this paper we formulate a discrete choice model that incorporates thresholds in the perception of changes in attribute values. The model considers multiple options and allows for changes in several attributes. We postulate that if thresholds exist they could be random, differ between individuals, and even be a function of socio-economic characteristics and choice conditions. Our formulation allows estimation of the parameters of the threshold probability distribution starting from information about choices.
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    Estimating the willingness-to-pay for road safety improvements
    (TAYLOR & FRANCIS LTD, 2006) Rizzi, Luis I.; Ortuzar, Juan de Dios
    The value of road safety is the fundamental input in social cost-benefit analysis of road safety schemes. It is also an increasingly important input in the social evaluation of almost any transport infrastructure project. This value is given by the amount that people are willing to pay for reducing the risk of a becoming a fatal victim or of suffering a serious injury. Traditionally, road safety willingness-to-pay has been estimated by means of contingent valuation and other surveys without making explicit reference to a particular travel demand context. The paper advocates the use of stated choice techniques that allow one to recreate the context of a particular trip customized to the respondent's past experience. For this and other reasons, it is argued that the proposed method is clearly superior to previous methods for estimating people's willingness-to-pay for improved road safety. The paper also provides a summary of the Chilean experience on road safety valuation using stated choice techniques; and it concludes by showing the importance of conducting local studies to elicit people's willingness to pay for safety.
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    Forecasting vs. observed outturn: Studying choice in faster inter-island connections
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) Maria Grisolia, Jose; Ortuzar, Juan de Dios
    Passenger demand and, in particular, mode choice between the islands of Gran Canaria and Tenerife has experienced important changes in the last decade. In 2005 the jetfoil, which had been the dominant mode for many years, was replaced by a slower but cheaper fast ferry service. This induced important changes in the market shares of all competing modes (airplane, slow ferry and another fast ferry with a shorter in-sea time, but needing a bus connection in land). We estimated several discrete choice models, with data collected two years before, with the aim to test their forecasting performance in relation with observed behaviour. Interestingly, we found that an easy to interpret multinomial logit model allowing for systematic taste variations performed best in forecasting. We also discuss some model assumptions related to forecasting that allow replicating the effects of introducing a new mode more accurately. We finally show how the model can be used to examine the social benefits of a related infrastructure improvement project in the island of Gran Canaria. (C) 2009 Elsevier Ltd. All rights reserved.
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    Identifying differences in willingness to pay due to dimensionality in stated choice experiments: a cross country analysis
    (ELSEVIER SCI LTD, 2009) Rose, John M.; Hensher, David A.; Caussade, Sebastian; Ortuzar, Juan de Dios; Jou, Rong Chang
    This paper explores the influence of both cultural and socio-economic characteristics on the perception of complexity and cognitive load associated with stated choice (SC) experiments. Complexity is analysed in terms of five design dimensions which were systematically varied according to a macro experimental design. To study the influence of cross country differences on willingness to pay estimates, we combined datasets collected in Sydney, Santiago de Chile and Taichung city in Taiwan, all of them related to an equivalent route choice experiment. Several mixed logit models were specified and estimated; our results show that design dimensions do have an impact on the behavioural outputs of discrete choice models estimated on SC data. However, these influences seem to be data-specific, suggesting that the impact of design dimensions upon SC Outcomes may be local and not necessarily transferable across different Countries and cultures. (C) 2008 Elsevier Ltd. All rights reserved.
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    Identifying transit driver preferences for work shift structures: An econometric analysis
    (INFORMS, 2008) Miranda, Felipe; Munoz, Juan Carlos; Ortuzar, Juan de Dios
    The combination of a strict labor legislation with daily and weekly time-dependent demand patterns has meant that transit companies tend to suffer significant inefficiencies; indeed, as more drivers than the minimum required are hired, providing services at off-peak periods, many tend to be inactive during these periods. To attack this problem, two strategies have been proposed. The first is using flexible shifts that may change daily according to a predefined contract. The other is using split shifts in which drivers' working hours are split in two to serve both the morning and afternoon peak periods. However, evidence of driver acceptance of these strategies is lacking.
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    Modeling discrete choices in the presence of inertia and serial correlation
    (INFORMS, 2007) Cantillo, Victor; Ortuzar, Juan de Dios; Williams, Huw C. W. L.
    The concept of habit or inertia in the context of (reluctance to) change in travel behavior has an important bearing on transport policy (e.g., how to break car use habits) and has remained an unresolved issue in demand modeling. Another major problem in modeling the response to policy measures is the potential correlation or dependence between the choices made by a given individual over time (i.e., serial correlation). The two phenomena are closely related. This paper discusses the effects of considering inertia and serial correlation on travel choices. We formulate a fairly general discrete choice model that incorporates randomly distributed inertia thresholds and allow for serial correlation. The inertia thresholds may also be a function of an individual's socioeconomic characteristics and choice conditions. The model can be applied with panel data as well as with mixed revealed and stated preference data. We applied it to real and simulated data, confirming that if these phenomena exist in the population but are not considered, serious errors in model estimation and prediction may arise, especially in the case of large policy impacts.
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    Modelling the demand for medium distance air travel with the mixed data estimation method
    (ELSEVIER SCI LTD, 2008) Ortuzar, Juan de Dios; Simonetti, Carolina
    A stated preference experiment is developed looking at airplane and a fictitious high-speed train trips between Santiago and Concepcion in Chile. Four variables are used - travel time, fare, comfort, and service delay; a factorial fractional design allowed the experimental size to be reduced to nine pairs of options. Trip characteristics and socio-economic information were also gathered for each respondent. With the purpose of overcoming the potential imperfections that pure SP models are known to have, we incorporated revealed preference data, obtained in a previous study, including bus, train and airplane travellers. Mixed stated and revealed preference models were estimated and compared with those obtained from the stated preference data alone. Finally, a second group of stated preference data is added. Different specifications were tested with mixed stated and revealed preference data. Moreover, by segmenting the sample we were able to derive subjective values of time for different kinds of individuals. (C) 2008 Elsevier Ltd. All rights reserved.
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    On the approximation bias to benefit measures in discrete choice models
    (IST EDITORIALI POLGRAFICI INT, 2008) Bowen, Cristian; Ortuzar, Juan de Dios; Rizzi, Luis I.
    We estimate the bias associated to using different approximations for calculating the benefits of transport projects. For this we generated a simulated databank that reproduces the real behaviour of a revealed preference sample on the choice of mode for work trips. Exact measures were computed for three transport policies differing in their degree of impact on mode choices. These values were then compared against the results of applying simpler but less precise measures, showing the existence of significant biases when classical explanatory models were considered. Significant biases were also detected when the correct methodology for marginal changes was applied in the presence of non-marginal policies. In the first case, the proportional error does not depend on the size of the policies, but in the second it grows with their impact. We also simulated another databank with non-linear utilities in income and calculated again some measures of welfare. We found that there are no significant biases if income effects are not considered. Neither did we find a systematic relation between these biases and the size (in terms of change) of the policy.
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    Valuing time with a joint mode choice-activity model
    (FABRIZIO SERRA EDITORE, 2006) Munizaga, Marcela A.; Correia, Rodrigo; Jara Diaz, Sergio R.; Ortuzar, Juan de Dios
    Activity and travel models share a common framework that cans for their joint estimation. This complex problem only recently has received attention in the literature. Explicit equations for travel choice and activity duration have been obtained, allowing disentangling the various components of the subjective value of time (travel time savings, resource value and value of assigning time to travel). Although it is natural to expect some interrelation between equations, only preliminary results assuming independence had been reported. We adapt a discrete/continuous econometric model and postulate a general error structure. We obtain more robust models, and value of time estimates significantly different and more credible.