The location of public logistic centers: an expanded capacity-limited fixed cost location-allocation modeling approach

The location problem considered in this paper concerns the optimal number, size, and location of public logistic centers. To solve this problem, a mathematical model is developed based on an expanded capacity-limited fixed cost location-allocation model of a network incorporating handling costs and the costs of the temporary storage of cargo in the logistic center. The effectiveness of the proposed approach is evaluated with a numerical example of locating public logistic centers of international importance in the Republic of Serbia, based on two scenarios regarding the future development of import cargo flows into the Republic to the year 2020.     

Optimizing location and capacity of rail-based Park-and-Ride sites to increase public transport usage

This paper presents a new methodology to identify optimal locations and capacity for rail-based Park-and-Ride (P&R) sites to increase public transport mode share. P&R is usually taken as an important component of policies for the sustainable development of urban transport systems. However, previous studies reveal that arbitrarily determined P&R sites may act to reduce public transport commuting. This paper proposes a methodology for the optimal location and capacity design of P&R sites, with the aim of enhancing public transport usage. A Combined Mode Split and Traffic Assignment (CMSTA) model is proposed for the P&R scheme. Taking the CMSTA model as the lower level, a bi-level mathematical programming model is then built to establish the optimal location and capacity of P&R sites. A heuristic genetic algorithm is adopted to solve this model. Finally, a network example is adopted to test numerically the proposed models and algorithms.     

基于港口枢纽处TOD公交站点选址模型的设计

本文针对中小型沿海城市提出的成本模型嵌入到公交站点优化方案中,构建各项成本的表达式,整合并建立以成本最小为目标的公交站点选址模型,对TOD公交站点的选址进行合理规划。此模型可有效运用到在中小型沿海城市中港口枢纽处的公交站点合理设置中,即实现乘客从轮渡到公交的零换乘,又能使港口枢纽对港口枢纽出入口与城市道路交汇处的交通现状影响达到最小,公交的通行能力达到最高。     

Modeling residential location choice in relation to housing location and road tolls on congested urban highway networks

We present a reformulation of the residential location submodel of the Integrated Model of Residential and Employment Location as a network equilibrium problem, thereby making travel costs by auto endogenous. The location of housing supply is examined as a welfare maximization problem for both user-optimal and system-optimal travel costs using concepts of bilevel programming. Finally, we briefly discuss how the employment submodel can be reformulated, and the entire model solved as a variational inequality problem.     

大型综合交通枢纽指路标志系统设置研究

城市大型综合交通枢纽由于其功能多样,辐射广泛,周边路网复杂,因此对其指路标志系统需要专门设计。文章以上海市虹桥综合交通枢纽指路标志系统为研究对象,从路网结构及交通流特性出发,将指路标志系统按出行者需求层次分为四级,并提出相应的指路标志设置原则及方法,供相关部门参考。     

Acquisition,efficiency and scale economies: An analysis of the British bus industry

The British Bus industry has undergone considerable transformation since privatization. Five major operators have emerged to dominate the market, a position almost exclusively attained through acquisition. This paper reviews the economies of scale argument commonly cited for this change and gives an overview of the acquisition process. It questions whether this argument gives a complete explanation for this industry development. For 58 individual companies, the level of technical efficiency attributable to firms operating at or near the optimum level of output is examined over 5 years to determine if mergers in practice have resulted in scale economies. Technical efficiency is estimated using data envelopment analysis, under assumptions of constant and variable returns to scale. Efficiency scores are then regressed on a time trend and a merger dummy to test whether acquired firms' efficiency has significantly improved above the average. It was found that over the period, efficiency had improved. This improvement, however, cannot be wholly attributed to the achievement of economies of scale. More specifically, there has been an improvement in the internal efficiency of acquired firms and some scale economies within group companies, the latter of which may have resulted from the eradication of competition.     

枢纽机场航线网络优化研究

枢纽机场航线网络优化主要解决由于航线网络结构与功能定位不匹配而导致的机场连通性低、航线网络同质化竞争严重、运行效率低下的问题。通过改进引力模型对城市对间的客流量进行预测,以此为预测的客流量为依据之一,以提高机场连通性为目的,构建航线网络优化模型,并进行求解。实现提高枢纽机场连通性、构建符合功能定位的层级网络的目标。并以位于我国中部,具有连接南北,贯穿东西地理优势的西安咸阳国际机场为例进行分析。由于国际航线受客观因素较多,本文主要研究国内客运航线,国际及货运不在本文研究之列。     

Regulatory policy and economies of scale in the U.S. intercity bus industry

After nearly a half century of federal and state regulation, the U.S. intercity bus industry is the subject of proposals which would drastically reduce the extent of governmental control over fare setting, service abandonment, and market entry. An essential requirement for understanding how these regulatory changes might affect the industry is knowing the extent to which economies of scale are present in the provision of intercity bus services. This paper reports on the analysis of economies of scale for both Class I firms and for Class II and III firms. The results show nearly constant returns to scale beyond very low output levels but very strong dependence on the mix of charter and regular-route service provided.     

基于物元分析法的城市轨道交通换乘枢纽评价

文章从换乘枢纽的适应性、合理性及人性化三个层面出发,建立了轨道交通换乘枢纽的评价指标体系,并利用熵值法确定评价指标的权重,建立了基于物元分析法的城市轨道交通换乘枢纽评价模型。通过实例应用分析,证明了该评价方法的有效性和可行性。     

Joint optimization of freight facility location and pavement infrastructure rehabilitation under network traffic equilibrium

Establishment of industry facilities often induces heavy vehicle traffic that exacerbates congestion and pavement deterioration in the neighboring highway network. While planning facility locations and land use developments, it is important to take into account the routing of freight vehicles, the impact on public traffic, as well as the planning of pavement rehabilitation. This paper presents an integrated facility location model that simultaneously considers traffic routing under congestion and pavement rehabilitation under deterioration. The objective is to minimize the total cost due to facility investment, transportation cost including traffic delay, and pavement life-cycle costs. Building upon analytical results on optimal pavement rehabilitation, the problem is formulated into a bi-level mixed-integer non-linear program (MINLP), with facility location, freight shipment routing and pavement rehabilitation decisions in the upper level and traffic equilibrium in the lower level. This problem is then reformulated into an equivalent single-level MINLP based on Karush–Kuhn–Tucker (KKT) conditions and approximation by piece-wise linear functions. Numerical experiments on hypothetical and empirical network examples are conducted to show performance of the proposed algorithm and to draw managerial insights.     

Work and home location: Possible role of social networks

This research explores to what extent people’s work locations are similar to that of those who live around them. Using the Longitudinal Employer-Household Dynamics data set and the 2000 decennial census, we investigate the home and work locations of different census block residents in the Twin Cities (Minneapolis-St. Paul) metropolitan area. Our aim is to investigate if people who share a residence neighborhood also share work locations to a degree beyond what would be explained by distanhe observed patterns is the role neighborhood level and work place social networks play in locating jobs and residences respectively.     

Dynamic location: an iconic model to synchronize temporal and spatial transportation data

This paper describes a model to synchronize the management and query of temporal and spatially referenced transportation data in geographic information systems (GIS). The model employs a method referred to as dynamic location, which facilitates spatial intersect queries from geographic shapes without the use of topological relationships. This is the inverse of how dynamic segmentation works in GIS. In contrast to dynamic segmentation, dynamic location stores geometry as an object within a single database field. This is an efficient, precise iconic model superseding the need for data decomposition into a complex set of tables. As an object model, the dynamic location process lends itself to high performance in an Internet, data-intensive, enterprise environment. Linear events are stored as {x, y} features, and not referenced to any route system. Route systems are built from {x, y, m} values (m for measure) and serve as number lines for mathematical operations. Any {x, y} object can then be referenced to either the Cartesian grid or any selected number line. This method offers the benefits of linear referencing, while making full use of a stable geodetic datum. Combinations of any {x, y} events may be placed over any {x, y, m} number line (route) and an intersect determined by looking through stacked {x, y, m} vertices of the coincident shapes. Since both geometry and shape reside in the same record, the use of “begin” and “end” dates facilitates full spatial and temporal version control. From a business process perspective, this creates a spatially enabled database, pulling GIS business functions back into the information technology mainstream.     

Reliable sensor deployment for network traffic surveillance

New sensor technologies enable synthesis of disaggregated vehicle information from multiple locations. This paper proposes a reliable facility location model to optimize traffic surveillance benefit from synthesized sensor pairs (e.g., for travel time estimation) in addition to individual sensor flow coverage (e.g., for traffic volume statistics), while considering probabilistic sensor failures. Customized greedy and Lagrangian relaxation algorithms are proposed to solve this problem, and their performance is discussed. Numerical results show that the proposed algorithms solve the problem efficiently. We also discuss managerial insights on how optimal sensor deployment and surveillance benefits vary with surveillance objective and system parameters (such as sensor failure probabilities).     

Biofuel refinery location and supply chain planning under traffic congestion

This research focuses on planning biofuel refinery locations where the total system cost for refinery investment, feedstock and product transportation and public travel is minimized. Shipment routing of both feedstock and product in the biofuel supply chain and the resulting traffic congestion impact are incorporated into the model to decide optimal locations of biofuel refineries. A Lagrangian relaxation based heuristic algorithm is introduced to obtain near-optimum feasible solutions efficiently. To further improve optimality, a branch-and-bound framework (with linear programming relaxation and Lagrangian relaxation bounding procedures) is developed. Numerical experiments with several testing examples demonstrate that the proposed algorithms solve the problem effectively. An empirical Illinois case study and a series of sensitivity analyses are conducted to show the effects of highway congestion on refinery location design and total system costs.     

Locating inspection facilities in traffic networks: an artificial intelligence approach

Abstract

In order for traffic authorities to attempt to prevent drink driving, check truck weight limits, driver hours and service regulations, hazardous leaks from trucks, and vehicle equipment safety, we need to find answers to the following questions: (a) What should be the total number of inspection stations in the traffic network? and (b) Where should these facilities be located? This paper develops a model to determine the locations of uncapacitated inspection stations in a traffic network. We analyze two different model formulations: a single-objective optimization problem and a multi-objective optimization problem. The problems are solved by the Bee Colony Optimization (BCO) method. The BCO algorithm belongs to the class of stochastic swarm optimization methods, inspired by the foraging habits of bees in the natural environment. The BCO algorithm is able to obtain the optimal value of objective functions in all test problems. The CPU times required to find the best solutions by the BCO are found to be acceptable.     

A vehicle manufacturer's view of the potential for electric automobiles

In the search for low pollution, low noise, multi‐fuel vehicles capable of adapting to almost any source of energy available, the electric vehicle continues to be suggested in a variety of forms. In the long‐term view, working on the hypothesis that either solar or nuclear energy can provide the only inexhaustible energy supplies, electric propulsion will undoubtedly have a significant role to perform, and it could provide a useful means of transport in the transition period out of the current dependency on crude oil.

There are, however, some grave question marks hanging over the viability of electric vehicles on a large scale both in terms of their energy efficiency and practicality. This paper describes the state of development and discusses the future prospects.     

工业管道声发射信号衰减测试及定位分析

简述了工业管道输送流体流动特性,以及声发射技术在管道检测中的应用。采用手持式声发射检测仪器配合不同频率传感器对在役工业管道进行检测,研究焊接有三通、法兰、阀门等外接接口的不规则管道的定位特征,对比分析规则管道与焊有外接接口的不规则管道衰减特征区别,通过对现场数据的分析,得到管道损伤定位与传播声速之间的相互关系以及不同传播速度条件下产生的定位误差,综合分析误差产生原因,作为对现场检测的经验。