Search results for "Transportation"
showing 10 items of 860 documents
Dissemination protocol for Heterogeneous Cooperative Vehicular Networks
2012
International audience; The difficulties associated with network connectivity, unreliable channels, and city environment characteristics make data dissemination task in vehicular urban networks a real challenge. Recently, some interesting solutions have been proposed to perform data dissemination in this environment. Starting from the analysis of these solutions, we present a new dissemination protocol named DHVN (Dissemination protocol for Heterogeneous Cooperative Vehicular Networks) that considers: (i) roads topology, (ii) network connectivity and possible partitioning in case of low traffic density, and (iii) heterogeneous communication capabilities of the vehicles. We compare our proto…
Dynamic routing-and-inventory problems: a review
1998
The paper presents a review of the available literature on a class of problems denoted as dynamic routing-and-inventory (DRAI) problems. They are characterized by the simultaneous relevance of routing and of inventory issues in a dynamic environment, within the framework of distribution logistics. A classification scheme is first proposed for these problems. Then the results obtained in this area are summarized. Finally, the papers available in the literature are clustered and discussed according to the proposed scheme.
ASSESSING USERS’ PERCEPTIONS OF FOUR TYPES OF ROAD SAFETY MEASURES
2022
Road crashes remain an important public health issue. This study aimed to assess the perceived importance of four types of measures for reducing traffic crash rates. For this cross-sectional study, data were obtained from a national sample of 1,200 Spanish drivers responding to a telephone-assisted survey. The most valued types of road safety measures were those related to users’ training/education and infrastructural improvements. Further, individual perceptions were influenced by both demographic and trip-related factors. The results of this study support the idea that user features remain a relevant issue to consider when developing and implementing road safety measures.
Similarity and Consistency in Hotel Online Ratings across Platforms
2019
Online ratings are a major driver of hotel choice. There are many ratings platforms, and the number of evaluations is huge. This article analyzes if hotel ratings vary across platforms, vary over time, and if consistency in ratings can be observed. Longitudinal online ratings taken from 11 platforms over a two-year period were analyzed through Self-Organizing Maps. The findings suggest a similar pattern of online ratings across most of the platforms, except for Yelp and HolidayCheck. In addition, the evaluation patterns are stable over time, and the analyzed attributes do not contribute decisively to explain the overall evaluation of hotels, which implies that tourists use a noncompensator…
L∞ estimates in optimal mass transportation
2016
We show that in any complete metric space the probability measures μ with compact and connected support are the ones having the property that the optimal transportation distance to any other probability measure ν living on the support of μ is bounded below by a positive function of the L∞ transportation distance between μ and ν. The function giving the lower bound depends only on the lower bound of the μ-measures of balls centered at the support of μ and on the cost function used in the optimal transport. We obtain an essentially sharp form of this function. In the case of strictly convex cost functions we show that a similar estimate holds on the level of optimal transport plans if and onl…
The collaborative consistent vehicle routing problem with workload balance
2021
Abstract The rising competition in the logistics sector forces companies to be more economically efficient. One of the major sources of inefficiency is the incomplete usage of available resources, such as vehicles’ capacities. Mechanism that allow to better exploit such resources by enabling carrier collaborations are on the rise. Our study examines a centrally organized multi-period collaborative vehicle routing problem, where carriers can exchange customers who have to be serviced on a regular basis. Collaborations, where carriers serve frequent customers, are supposed to face the problem of (i) time consistency in terms of visiting time, and of (ii) service consistency. The latter ensure…
Branch-and-Cut-and-Price for the Vehicle Routing Problem with Time Windows and Convex Node Costs
2019
Two critical yet frequently conflicting objectives for logistics and transportation service companies are improving customer satisfaction and reducing transportation cost. In particular, given a network of customer requests with preferred service times, it is very challenging to find vehicle routes and service schedules simultaneously that respect all operating constraints and minimize the total transportation and customers’ inconvenience costs. In this paper, we introduce the vehicle routing problem with time windows and convex node costs (VRPTW-CNC), in which we model each customer’s inconvenience cost as a convex function of the service start time at that customer. The VRPTW-CNC combine…
Multi-Connectivity Management for 5G V2X Communication
2019
With the advent of automated driving functions the need for cooperation among vehicles becomes increasingly necessary. The availability of high quality connectivity is an important factor for successful and uninterrupted cooperative and autonomous services. Flexible selection of available connectivity options, increases the probabilities to achieve and maintain the required Quality of Service (QoS). Future vehicles will support multiple 5G communication interfaces e.g., cellular (Uu), sidelink (PC5). A 5G RAN-based solution is proposed in this paper to dynamically select and change the communication interface that is suitable for a V2X service, considering radio and road conditions. The com…
Understanding the Key Factors of Shared Mobility Services: Palermo as a Case Study
2020
The potential success of shared mobility services in the urban area strongly depends on careful tariff planning, adequate sizing of the fleet and efficient integrated public transport system, as well as on the application of policies in favor of sustainable modes of transport. The balance between earnings and expenses is not always an easy target for the companies in those cities where these services are not well-rooted in the citizens’ mobility habits. Often only large operators in the sector can continue to offer a service generating profit. However, several factors can determine the success or the failure of shared mobility services. The objective of this study is to identify, thanks to …
Vertical take-off and landing air transport to provide tourist mobility.
2012
Abstract This paper examines helicopter transfer services to reach attractive and not very accessible tourist areas, taking Sicily and its minor islands, in the South of Italy, as a case study. We investigate the viability of helicopter scheduled services for tourists moving from/to airports or doing one day tours to visit far away places. The mode choice of tourists is simulated using random utility models employing stated preference data. Heli-shuttle service is planned in terms of fleet size, frequency, fare and location pattern of heliports. The paper also analyses how a public subsidy reducing fares might change the set of feasible connections.