Search results for "050210 logistics & transportation"
showing 10 items of 331 documents
Online shortest paths with confidence intervals for routing in a time varying random network
2018
International audience; The increase in the world's population and rising standards of living is leading to an ever-increasing number of vehicles on the roads, and with it ever-increasing difficulties in traffic management. This traffic management in transport networks can be clearly optimized by using information and communication technologies referred as Intelligent Transport Systems (ITS). This management problem is usually reformulated as finding the shortest path in a time varying random graph. In this article, an online shortest path computation using stochastic gradient descent is proposed. This routing algorithm for ITS traffic management is based on the online Frank-Wolfe approach.…
'Not as safe as I believed': Differences in perceived and self-reported cycling behavior between riders and non-riders
2021
Cycling behavior remains a key issue for explaining several traffic causalities occurring every day. However, recent studies have shown how the assessment of the own safety-related behaviors on the road may substantially differ from how third parties assess them. Thus, the aim of this study was to evaluate the differences between cyclists’ self-reported behavior and the proxy-reported behavior that other (non-cyclist) road users perceive from bike riders. For this purpose, this study used data from two samples: (i) 1064 cyclists (M = 32.83 years) answering the Cycling Behavior Questionnaire—CBQ, and (ii) 1070 non-cyclists (M = 30.83 years) answering an adapted version of the CBQ for externa…
Evaluation of Roundabout Safety Performance through Surrogate Safety Measures from Microsimulation
2018
The paper presents a microsimulation-based approach for roundabout safety performance evaluation. Based on a sample of Slovenian roundabouts, the vehicle trajectories exported from AIMSUN and VISSIM were used to estimate traffic conflicts using the Surrogate Safety Assessment Model (SSAM). AIMSUN and VISSIM were calibrated for single-lane, double-lane and turbo roundabouts using the corresponding empirical capacity function which included critical and follow-up headways estimated through meta-analysis. Based on calibration of the microsimulation models, a crash prediction model from simulated peak hour conflicts for a sample of Slovenian roundabouts was developed. A generalized linear model…
Urban smart mobility in the scientific literature — bibliometric analysis
2018
Abstract This article aims at identification of the main trends in scientific literature characterising urban smart mobility, on the basis of bibliometric analysis of articles published in the ISI Web of Science and Scopus databases. The study period was set from 2000 to 2017. Authors used a basic technique of the bibliometric analysis of the scientific literature characterising urban smart mobility with the support of the VOSviewer software. The analysis included the number of publications, citation analysis, research area analysis and the most frequent keywords. The analysis led to taking notice of current research trends dealing with the urban smart mobility. The core of the paper is a t…
Public Policies to Promote Sustainable Transports : Lessons from Valencia
2021
Bicycling appears in the literature on urban mobility as a more sustainable transportation mode for future transportation, based on empirical evidence of the potential benefits of bicycling on the environment, society, and health. In this context, public interventions to promote and maintain bicycling as a sustainable practice and its positive effects are salient. This article reviews different cycling policies with respect to cycling facilities present in the literature and compares them with a case study in Valencia (Spain). We collected information on the public policies implemented in Valencia and the traffic intensity in bike lanes over detecting loops distributed around the city. The …
The Association Between Transportation and Life-Space Mobility in Community-Dwelling Older People With or Without Walking Difficulties.
2016
Objective: The aim of this study is to examine whether a persons’ most frequently used mode of transportation is associated with life-space mobility and whether the association differs between persons with or without walking difficulties. Method: Life-space mobility was measured with the Life-Space Assessment in 848 community-dwelling men and women aged 75 to 90 years. Six separate mobility groups were formed according to the most frequently used mode of transportation (car driver, car passenger, public transportation) combined with the presence or absence of difficulties walking 2 km. Results: Car drivers without walking difficulties had the highest life-space mobility scores, and car pas…
Bi-objective multi-layer location–allocation model for the immediate aftermath of sudden-onset disasters
2019
International audience; Locating distribution centers is critical for humanitarians in the immediate aftermath of a sudden-onset disaster. A major challenge lies in balancing the complexity and uncertainty of the problem with time and resource constraints. To address this problem, we propose a location–allocation model that divides the topography of affected areas into multiple layers; considers constrained number and capacity of facilities and fleets; and allows decision-makers to explore trade-offs between response time and logistics costs. To illustrate our theoretical work, we apply the model to a real dataset from the 2015 Nepal earthquake response. For this case, our method results in…
Risky choices in strategic environments: An experimental investigation of a real options game
2019
Managers frequently make decisions under conditions of fundamental uncertainty due the stochastic nature of the outcomes and competitive rivalry. In this study, we experimentally test a theoretical model under fundamental uncertainty and competitive rivalry by designing a sequential interaction game between two players. The first mover can decide either to choose a sure outcome that assigns a risky outcome to the second mover or to pass the decision to the second mover. If the second player gets the chance to decide, she can choose between a sure outcome, conditioned by the assignment of a risky payoff to the first mover, or the sharing of the risky outcome with the first mover. We then int…
The Hierarchical Mixed Rural Postman Problem: Polyhedral analysis and a branch-and-cut algorithm
2017
[EN] The Hierarchical Mixed Rural Postman Problem is defined on a mixed graph where arcs and edges that require a service are divided into clusters' that have to be serviced in a hierarchical order. The problem generalizes the Mixed Rural Postman Problem and thus is NP-hard. In this paper, we provide a polyhedral analysis of the problem and propose a branch-and-cut algorithm for its solution based on the introduced classes of valid inequalities. Extensive computational experiments are reported on benchmark instances. The exact approach allows to find the optimal solutions in less than 1 hour for instances with up to 999 vertices, 2678 links, and five clusters.
Optimizing the level of service quality of a bike-sharing system
2016
Public bike-sharing programs have been deployed in hundreds of cities worldwide, improving mobility in a socially equitable and environmentally sustainable way. However, the quality of the service is drastically affected by imbalances in the distribution of bicycles among stations. We address this problem in two stages. First, we estimate the unsatisfied demand (lack of free lockers or lack of bicycles) at each station for a given time period in the future and for each possible number of bicycles at the beginning of the period. In a second stage, we use these estimates to guide our redistribution algorithms. Computational results using real data from the bike-sharing system in Palma de Mall…