Browsing by Author "de Grange, Louis"

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    A consolidated model of trip distribution
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) de Grange, Louis; Fernandez, Enrique; de Cea, Joaquin
    This work analyzes and compares various trip distribution models with spatial aggregation within a common theoretical framework for formulating and solving multi-objective optimization problems. A new model is designed that incorporates the main characteristics of existing ones. These models are then calibrated with a single database at different spatial aggregation levels using maximum likelihood. The results show that with aggregated data the various models differ little, but with disaggregated data the differences are considerable. It is also demonstrated that changing the level of data aggregation can significantly alter the models' parameter values. (C) 2009 Elsevier Ltd. All rights reserved.
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    An equivalent optimization formulation for the traffic assignment problem with asymmetric linear costs
    (TAYLOR & FRANCIS LTD, 2009) de Grange, Louis; Carlos Munoz, Juan
    In this paper, we present a general formulation for the deterministic traffic assignment problem, using an equivalent optimization problem applicable to the case of asymmetric linear cost functions. We present a resolution approach for this problem in such a way that in equilibrium Wardrop's first principle or Nash equilibrium is satisfied. We conclude that many deterministic traffic assignment problems with asymmetric linear costs can be formulated as an optimization problem whose objective is defined by a line integral, and whose constraints correspond to non-negativity and flows conservation. By adequately defining the integration path, it is feasible to resolve the problem, obtaining Wardrop's equilibrium. This approach can be applied in other economic contexts, including microeconomic theory and consumer surplus analysis.
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    Combined Model Calibration and Spatial Aggregation
    (2010) de Grange, Louis; Fernandez, Enrique; de Cea, Joaquin; Irrazabal, Magdalena
    A methodology is proposed for estimating a combined transportation model that accommodates spatial aggregation. It employs maximum likelihood estimation using a joint probability function that includes destination and mode choice simultaneously. The main contribution of the paper is the incorporation of a spatial aggregation strategy to validate the method when the survey data are insufficient. By aggregating small zones into larger districts, estimation of the trip distribution parameters can be achieved with limited data, while mode choice continues to be estimated using disaggregated data. Our results demonstrate that including trip distribution in the travel decision induces variations in the utility function parameter estimators obtained for the different travel modes when only mode choice is estimated. The methodology thus corrects omission bias.
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    Effects of environmental alerts and pre-emergencies on pollutant concentrations in Santiago, Chile
    (PERGAMON-ELSEVIER SCIENCE LTD, 2012) Troncoso, Rodrigo; de Grange, Louis; Cifuentes, Luis A.
    To reduce air pollution levels in Santiago, Chile on days when the weather is expected to create poor ventilation conditions and increased air pollutant concentrations, the responsible authorities impose temporary restrictions on motor vehicles and certain industrial activities. We estimate the impact of these restrictions on the city's air quality using data collected by a network of monitoring stations. The estimates show that the restrictions do reduce the average concentrations of coarse and fine particulate matter, carbon monoxide and nitrogen oxide (both gases are emitted mainly by vehicles). However, no significant changes were found in the sulfur dioxide concentrations, which are primarily the result of industrial processes. (C) 2012 Elsevier Ltd. All rights reserved.