28 research outputs found

    Un modelo para resolver el problema dinámico de despacho de vehículos con incertidumbre de clientes y con tiempos de viaje en arcos

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    Indexación: Web of Science; ScieloIn a real world case scenario, customer demands are requested at any time of the day requiring services that are not known in advance such as delivery or repairing equipment. This is called Dynamic Vehicle Routing (DVR) with customer uncertainty environment. The link travel time for the roadway network varies with time as traffic fluctuates adding an additional component to the dynamic environment. This paper presents a model for solving the DVR problem while combining these two dynamic aspects (customer uncertainty and link travel time). The proposed model employs Greedy, Insertion, and Ant Colony Optimization algorithms. The Greedy algorithm is utilized for constructing new routes with existing customers, and the remaining two algorithms are employed for rerouting as new customer demands appear. A real world application is presented to simulate vehicle routing in a dynamic environment for the city of Taipei, Taiwan. The simulation shows that the model can successfully plan vehicle routes to satisfy all customer demands and help managers in the decision making process.En un escenario real, los pedidos de los clientes son solicitados a cualquier hora del día requiriendo servicios que no han sido planificados con antelación tales como los despachos o la reparación de equipos. Esto es llamado ruteo dinámico de vehículos (RDV) considerando un ambiente con incertidumbre de clientes. El tiempo de viaje en una red vial varía con el tiempo a medida que el tráfico vehicular fluctúa agregando una componente adicional al ambiente dinámico. Este artículo propone un modelo para resolver el problema RDV combinando estos dos aspectos dinámicos. El modelo propuesto utiliza los algoritmos Greedy, Inserción y optimización basada en colonias de hormigas. El algoritmo Greedy es utilizado para construir nuevas rutas con los clientes existentes y los otros dos algoritmos son usados para rutear vehículos a medida que surjan nuevos clientes con sus respectivos pedidos. Además, se presenta una aplicación real para simular el ruteo vehicular en un ambiente dinámico para la ciudad de Taipei, Taiwán. Esta simulación muestra que el modelo es capaz de planificar exitosamente las rutas vehiculares satisfaciendo los pedidos de los clientes y de ayudar los gerentes en el proceso de toma de decisiones.http://ref.scielo.org/3ryfh

    A Decision-Rule Topological Map-Matching Algorithm with Multiple Spatial Data

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    Towards a parameter tuning approach for a map-matching algorithm

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    Children at risk: a comparison of child pedestrian traffic collisions in santiago, chile and seoul, south korea

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    Objective: We examine and compare pedestrian-vehicle collisions and injury outcomes involving school-age children between 5 and 18 years of age in the capital cities of Santiago, Chile and Seoul, South Korea. Methods: We conduct descriptive analysis of the child pedestrian-vehicle collision (P-VC) data (904 collisions for Santiago, and 3,505 for Seoul) reported by the police between 2010 and 2011. We also statistically analyze factors associated with child P-VCs, both by incident severity and age group using three regression models: negative binomial, probit, and spatial lag models. Results: Descriptive statistics suggest that child pedestrians in Seoul have a higher risk of being involved in traffic crashes than their counterparts in Santiago. However, in Seoul a greater proportion of children are unharmed as a result of these incidents, while more child pedestrians are killed in Santiago. Younger children in Seoul suffer more injuries from P-VCs than in Santiago. The majority of P-VCs in both cities tend to occur in the afternoon and evening, at intersections in Santiago and at midblock locations in Seoul. Our model results suggest that the resident population of children is positively associated with P-VCs in both cities, and school concentrations apparently increase P-VC risk among older children in Santiago. Bus stops are associated with higher P-VCs in Seoul, while subway stations relate with higher P-VCs among older children in Santiago. Zone-level land use mix was negatively related to child P-VCs in Seoul, but not in Santiago. Arterial roads are associated with fewer P-VCs, especially for younger children in both cities. A share of collector roads is associated with increased P-VCs in Seoul, but fewer P-VCs in Santiago. Hilliness is related to fewer P-VCs in both cities. Differences in these model results for Santiago and Seoul warrant additional analysis as do the differences in results across model type (Negative Binomial versus Spatial Lag models). Conclusions: To reduce child P-VCs, this study suggests the need to assess: subway station and bus stop area conditions in Santiago and Seoul, respectively; areas with high density of schools in Santiago; areas with greater concentrations of children in both cities; and collector roads in Seoul.MIT International Science and Technology Initiatives. MIT-Chile Seed FundUniversidad Andres Bello (Project DI-533-14/R

    A qualidade das ferramentas de geocodificação automática: um estudo utilizando endereços de prontuários hospitalares em Temuco, Chile

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    Automatic geocoding methods have become popular in recent years, facilitating the study of the association between health outcomes and the place of living. However, rather few studies have evaluated geocoding quality, with most of them being performed in the US and Europe. This article aims to compare the quality of three automatic online geocoding tools against a reference method. A subsample of 300 handwritten addresses from hospital records was geocoded using Bing, Google Earth, and Google Maps. Match rates were higher (> 80%) for Google Maps and Google Earth compared with Bing. However, the accuracy of the addresses was better for Bing with a larger proportion (> 70%) of addresses with positional errors below 20m. Generally, performance did not vary for each method for different socioeconomic status. Overall, the methods showed an acceptable, but heterogeneous performance, which may be a warning against the use of automatic methods without assessing quality in other municipalities, particularly in Chile and Latin America

    Use of data imputation tools to reconstruct incomplete air quality datasets:a case-study in Temuco, Chile

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    © 2018 Elsevier LtdMissing data from air quality datasets is a common problem, but is much more severe in small cities or localities. This poses a great challenge for environmental epidemiology as high exposures to pollutants worldwide occur in these settings and gaps in datasets hinder health studies that could later inform local and international policies. Here, we propose the use of imputation methods as a tool to reconstruct air quality datasets and have applied this approach to an air quality dataset in Temuco, a mid-size city in Chile as a case-study. We attempted to reconstruct the database comparing five approaches: mean imputation, conditional mean imputation, K-Nearest Neighbor imputation, multiple imputation and Bayesian Principal Component Analysis imputation. As a base for the imputation methods, linear regression models were fitted for PM2.5 against other air quality and meteorological variables. Methods were challenged against validation sets where data was removed arti

    Children at risk: an initial comparison of child pedestrian traffic collisions in Santiago, Chile and Seoul, South Korea

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    We examine pedestrian traffic collisions involving children in Santiago de Chile and Seoul, Korea in 2010-2011. Descriptive statistics suggest that children in Seoul have a higher risk of being involved in accidents than their counterparts in Santiago; although in Seoul a higher share of children escape without injury than in Santiago. Both cities have temporal patterns unsurprisingly consistent with the school day and school years; although Seoul has slightly lower winter rates. Exploratory regression models reveal varying relationships between different measures of the built form and transportation system and accident density and risk, although further model development is needed.  

    Children at risk: an initial comparison of child pedestrian traffic collisions in Santiago, Chile and Seoul, South Korea

    No full text
    We examine pedestrian traffic collisions involving children in Santiago de Chile and Seoul, Korea in 2010-2011. Descriptive statistics suggest that children in Seoul have a higher risk of being involved in accidents than their counterparts in Santiago; although in Seoul a higher share of children escape without injury than in Santiago. Both cities have temporal patterns unsurprisingly consistent with the school day and school years; although Seoul has slightly lower winter rates. Exploratory regression models reveal varying relationships between different measures of the built form and transportation system and accident density and risk, although further model development is needed.  
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