Improved approaches to the network design problem in regional hazardous waste management systems

This paper investigates the network design problem arising from the regional hazardous waste management system. The problem is to identify the locations of various waste facilities, and determine the transportation routes of hazardous wastes and waste residues between those waste facilities. Aiming at minimizing jointly the total cost and total risk, the problem is formulated as a multi-objective mixed integer linear programming model. By exploiting the advantages of the model, three multi-objective optimization approaches are customized to find highly qualified non-dominated solutions. The effectiveness and efficiency of the approaches are examined both on a hypothetical case and a realistic case.     

From XXS to XXL: Towards a typology of distribution centre facilities

Distribution centres are becoming more and more relevant for spatial planning, due to their rapidly increasing size and number. There is little literature, however, that provides a generalized analysis of the size and functional attributes of distribution centres, and none that discusses the relationships between these attributes. Our aim is to fill this gap by providing new evidence and analysis to understand this relationship. We make use of an extensive database of 2888 DCs in the Netherlands to develop a new typology of DCs based on the geographical location of DCs, their functional attributes and client sector characteristics. The analysis shows that the context in which medium sized DCs are operating is more heterogeneous than in the case of very large and small size DCs. This study is a first attempt to analyse this relationship between facility size and functions based on a rich and extensive dataset of large population of DCs. The results can serve as input for further quantitative statistical analysis and international comparison.     

The time constrained multi-commodity network flow problem and its application to liner shipping network design

The multi-commodity network flow problem is an important sub-problem in several heuristics and exact methods for designing route networks for container ships. The sub-problem decides how cargoes should be transported through the network provided by shipping routes. This paper studies the multi-commodity network flow problem with transit time constraints which puts limits on the duration of the transit of the commodities through the network. It is shown that for the particular application it does not increase the solution time to include the transit time constraints and that including the transit time is essential to offer customers a competitive product.     

From colonization to national territories in continental West Africa: the historical geography of a transport infrastructure network

This paper argues that in order to study the geohistory of a transport infrastructure network it is necessary to identify the link between networks and territorial scales during a given period. It focuses on the creation of road and rail networks in French West Africa during the colonial period and in the land-locked States during the national period, which involves post-independence development policies. The network is perceived in this paper as the manifestation of the political will to facilitate traffic within a delimited space. Within the colonial and then the national periods roads and railways were thus constructed as part of a process that can be interpreted as the outcome of a compromise between a territorial project and the capacity to implement it. This geohistorical study thus allows us to identify, with reference to the link between borders and networks, the successive geographical linkages (railway and port combinations with their subsequent branches, national roads, economic roads, external connections) which have been applied in the delimited spaces in question. This exercise has concentrated particularly on continental West Africa.     

An accelerated Benders decomposition algorithm for sustainable supply chain network design under uncertainty: A case study of medical needle and syringe supply chain

This paper proposes a multi-objective possibilistic programming model to design a sustainable medical supply chain network under uncertainty considering conflicting economic, environmental and social objectives. Effective social and environmental life cycle assessment-based methods are incorporated in the model to estimate the relevant environmental and social impacts. An accelerated Benders decomposition algorithm utilizing three efficient acceleration mechanisms is devised to cope with computational complexity of solving the proposed model. Computational analysis is also provided by using a medical industrial case study to present the significance of the proposed model as well as the efficiency of the accelerated Benders decomposition algorithm.     

Evaluating energy efficiency for airlines: An application of VFB-DEA

In this paper, the energy efficiency of airlines has been studied with number of employees, capital stock and tons of aviation kerosene as the inputs and Revenue Ton Kilometers, Revenue Passenger Kilometers, total business income and CO₂ emissions decrease index as the outputs. A new model, Virtual Frontier Benevolent DEA Cross Efficiency model (VFB-DEA), is proposed to calculate the energy efficiencies of 11 airlines from 2008 to 2012. Spearman correlation coefficient is applied to validate the applicability of the new model. The results indicate that capital efficiency is an important factor in driving energy efficiency, and the American financial crisis had a significant influence on the change in energy efficiency during this period.     

Megaquarry versus decentralized mineral production: network analysis of cement production in the Great Lakes region,USA

The geography of mineral resources and human settlement influences the production–consumption cycle of cement and other mined construction materials, and affects the energy, cost and environmental burden associated with these materials. Although mines that supply most construction products have traditionally been located near major points of consumption, population pressures have raised the possibility that these small, widely scattered operations might be replaced by large, megaquarry operations. This study uses network analysis to compare transportation-related energy and cost for cement production from highly centralized facilities, or megaquarries, to that from smaller production facilities dispersed throughout the Great Lakes region of the United States. Results show that a transition to megaquarries can increase transport-related energy and associated environmental impacts by almost 50%. This suggests that decisions involving the location of mining operations for construction products are best made on a regional rather than local basis.     

The distribution network of Amazon and the footprint of freight digitalization

The emergence of e-commerce as a dominant retail paradigm is associated with a rapid shift in the commercial footprint towards distributional-based consumption. Through the analysis of the geographical expansion, market coverage, and functional specialization of Amazon's distribution network, the research underlines that digitalization has a pronounced physicality. E-commerce is favoring a transition from the conventional retail freight landscape towards a new physicality of freight distributions involving purpose-designed facilities, modes, and channels. The case of Amazon underlines a consistent locational behavior to achieve a distributional hierarchy of facilities granting logistical access to consumer markets. The distributional hierarchy is organized in three stages, which are procurement and fulfillment, distribution, and last-mile.     

An estimation of returns to scale of airport airsides under multiple optimal solutions in DEA

The returns to scale (RTS) nature of 37 Chinese airport airsides are investigated in this paper. Multiple optimal solutions in DEA (Data Envelopment Analysis) models may lead to error RTS estimation. To address this problem, we use the (Zhu and Shen, 1995) RTS method. The empirical study shows that all those airsides with two runways operate under decreasing RTS and those airsides with only one runway either operate in the area of increasing RTS or in the area of constant RTS.     

Effect of street network design on traffic congestion and traffic safety

We examine the effects of street network design on congestion levels and crash rates in neighborhoods across Utah's Wasatch Front. We employ propensity score matching to select pairwise neighborhood samples that have other similar characteristics but differ greatly in street network design. Our results show that denser and more connected neighborhoods have significantly lower congestion levels, but they do not have measurably lower (or higher) crash rates, presumably due to the prevalence of four-way intersections. This study can help guide data-driven decision making on street network design standards for many of the growing urban areas across the country and globe.     

Financial distress,survival network design strategies,and airline pricing: An event study of a merger between a bankrupt FSC and an LCC in Brazil

This paper develops an event study to investigate the airfare effects of the bankruptcy of a financially distressed full-service carrier (FSC) and its subsequent acquisition by a low-cost carrier (LCC) in Brazil. We account for the distressed carrier's survival network design strategies (SNDS) pursued during its reorganization—a suspected source of sample selection bias. Additionally, as rivals' pricing could be aimed at driving the distressed/bankrupt carrier out of the market, we treat the carrier's distress as endogenously determined with it. Our results do not uncover any survival pricing behavior stemming from SNDS, but reveal fiercer price competition from rivals in periods preceding both the distressed carrier's bankruptcy filing and acquisition. We also find evidence of enduring price competitiveness in the long run of the acquisition event, shedding light on the potential facilitating role played by bankruptcy protection regulations in keeping and sustaining market contestability after the bankruptcy-filing period.     

Concurrent design of product family and supply chain network considering quality and price

We study the problem of concurrent design of a product family and its supply chain (SC) network. Inspired by a real-life case in computer industry, the impact of quality and price in SC demand is investigated. Two different models are proposed, the former maximizes the company’s profit with respect to customers’ priorities on quality and price; the latter is a bi-objective programming, which consider two extreme customer groups: for one group quality has the highest priority and for the other price; the intermediate groups falls between these two. The performance of the models is analyzed through a case problem.     

Comparing paratransit in seven major African cities: An accessibility and network analysis

Accessibility to transit, together with other important system characteristics such as network coverage and frequency, is a crucial driver of modal choice for urban commuting. In turn, commuting is a major driver of energy consumption and of socio-environmental externalities in cities. So far, few quantitative and comparative assessments of paratransit in cities of Africa have been carried out due to data scarcity and the prevalence of informal services. Here we leverage the recent release of General Transit Feed Specification (GTFS) data to produce comparative metrics of accessibility, network, and service quality of paratransit in seven major cities in sub-Saharan Africa (Abidjan, Accra, Addis Ababa, Freetown, Harare, Kampala, Nairobi). Our results allow for a first-order assessment and comparison of different crucial paratransit characteristics in these cities, shedding light on transport inequality and urban segregation dynamics. The analysis and metrics produced can support transport systems planners in major cities of low-income countries. Further research should focus on approaches for overcoming the residual data limitations and expand the quantitative understanding of paratransit.     

Fleet deployment, network design and hub location of liner shipping companies

A mixed integer linear programming formulation is proposed for the simultaneous design of network and fleet deployment of a deep-sea liner service provider. The underlying network design problem is based on a 4-index (5-index by considering capacity type) formulation of the hub location problem which are known for their tightness. The demand is elastic in the sense that the service provider can accept any fraction of the origin–destination demand. We then propose a primal decomposition method to solve instances of the problem to optimality. Numerical results confirm superiority of our approach in comparison with a general-purpose mixed integer programming solver.     

The effect of a roundabout corridor's design on selecting the optimal crosswalk location: A multi-objective impact analysis

Crosswalks located at mid-block segment between roundabouts can provide a good balance among delay, carbon dioxide (CO₂) emissions, and relative difference between vehicles and pedestrians speed. However, when considering local pollutant criteria, the optimal crosswalk location may be different to that obtained for CO₂. This paper described a multi-objective analysis of pedestrian crosswalk locations, with the objectives of minimizing delay, emissions, and relative difference between vehicles and pedestrians speed. Accounting for the difference between global (e.g., CO₂) and local pollutants (monoxide carbon, nitrogen oxides, and hydrocarbons) was one the main considerations of this work. Vehicle activity along with traffic and pedestrian flows data at six roundabout corridors in Portugal, one in Spain, and one in the United States were collected and extracted. A simulation environment using VISSIM, Vehicle Specific Power, and Surrogate Safety Assessment Model models was used to evaluate traffic operations along the sites. The Fast Non-Dominated Sorting Genetic Algorithm (NSGA-II) was implemented to further search optimal crosswalk locations. The results yielded improvements to both delay and emissions by using site-optimized crosswalks. The findings also revealed that the spacing between intersections widely influenced the optimal crosswalk location along a mid-block section. If the spacing is low (<100 m), the crosswalk location will be approximately in 20%–30% of the spacing length. For spacing values between 140 and 200 m, crosswalks would be located at the midway position. When a specific pollutant criterion was considered, no significant differences were observed among optimal crosswalk data sets.     

Urban growth and freight transport: From sprawl to distension

This paper aims at discussing the effects of the urban growth on freight mobility through the analysis of urban activities localisation. Thanks to the results of this work, we lay the basics of an original concept that synthetizes logistics sprawl and other localisation dynamics taking into principal consideration the mobility of freight in general: the logistics distension.Through the spatial analysis of activities and population localisation between 1982 and 2012 in Lyon's urban area, we show the evolution of the socio-economic morphology and evolution of the freight landscape. Through freight movements modelling, we show the evolution of freight mobility in the conurbation of Lyon with regard to the modifications of the urban fabric.     

关于铁路枢纽联络线与疏解线的设计分析

铁路联络线和疏解线是铁路路网不可缺少的组成部分,线路不长但用途很大,在新线设计尤其是枢纽设计中经常遇到。联络线的标准一般应与相邻线的标准一致;疏解线的标准由于其特殊性．在设计规范中规定了最小曲线半径和最大纵坡。站场设计手册对枢纽的疏解方式做了一些归类与分析,但设计者只知道这些还远远不够。随着枢纽引入线路的增多,联络线与疏解线会越来越复杂,既涉及到如何节省工程投资,更涉及到运输安全、质量与效率。分析铁路枢纽联络线与疏解线的设计方法,以便更好地设计这类线路。     

Locating manufacturing and distribution centers: An integrated supply chain-based spatial interaction approach

This study investigates the facility location problem of transnational personal computer (PC) manufacturing for the domestic market of China. An integrated supply chain-based spatial interaction model is formulated to determine facility locations of the transnational PC manufacturing centers and regional product distribution centers in China, with the goal of maximizing the potential rate of return on facility investment. The numerical results show that the Shanghai municipality is ranked highest for siting both the manufacturing and distribution centers for a transnational PC manufacturing enterprise.     

An analysis of drivers route choice behaviour using GPS data and optimal alternatives

This work aims to study drivers' route choices using a dataset of low frequency GPS coordinates to identify travels' trajectories. The sample consists of 89 drivers who performed 42 thousand paths in the province of Reggio Emilia, in Italy, during the seventeen considered months. Four attributes that may be important for the driver are identified and four optimal alternative paths are created based on the selected objectives to evaluate route choice behaviour. The comparison between the characteristics of the paths allows to conclude that drivers select routes that are overall longer than their optimal alternatives but that allow for higher speeds. Furthermore the statistical analysis of drivers' route choices in macroareas evidences that drivers have different behaviours depending on the geography of the territory. Specifically, there is higher heterogeneity of route choices in the plain areas compared to the mountains. In the second part of this work, clusters of repetitive travels are identified and a Geographical Route Directness Index is proposed to identify the areas of the province where the deviation from the shortest alternative path is higher. The analysis shows that, among groups of repetitive travels, the value of the index is higher along the ring road of the city of Reggio Emilia and there is a strong negative correlation between the frequency the driver selects the longer alternative that allow for higher speed, and the number of additional kilometres the same driver has to travel.