A stochastic programming winner determination model for truckload procurement under shipment uncertainty

We propose a two-stage stochastic integer programming model for the winner determination problem (WDP) in combinatorial auctions to hedge the shipper’s risk under shipment uncertainty. The shipper allows bids on combinations of lanes and solves the WDP to determine which carriers are to be awarded lanes. In addition, many other important comprehensive business side constraints are included in the model. We demonstrate the value of the stochastic solution over one obtained by a deterministic model based on using average shipment volumes. Computational results are given that indicate that moderately sized realistic instances can be solved by commercial branch and bound solvers in reasonable time.     

A strategic approach to improve sustainability in transportation service procurement

This paper focuses on the procurement of full truck-load transportation service with the view to ensuring sustainability in transport logistics. The carrier assignment problem (CAP) involved in truck load contract auction is studied using a complete enumeration method and heuristic approach. Performance of both methods is compared in terms of solution quality and computational time based on the results of sample problems considered. Also, the impact of combinatorial bidding on reducing empty haul in real world case is analyzed and environmental sustainability is achieved through reduction in carbon foot print.     

Monitoring social network formation and information content analysis of transport anomalies: The case of airline crashes

Airliners' industry corresponds to an extremely sensitive and volatile sector, especially subject to information related to flight safety. Possible negative publicity on such issues may result to sudden and abrupt fluctuations of air travel demand, accompanied with phenomena of panic or feelings of generalized insecurity. The proliferation of social media platforms that offer a direct and immediate two-way communication channel contributes to the overall information propagation related to flights security (as exposed in the recent airlines crashes) and can be viewed as a proxy of the social network formation of such paradigms. The current paper aims to offer a framework for quantitatively analyzing social network formation, based on comprehensive network metrics, valuable in cases of commercial airliners accidents. Moreover, the use of data from social media connectivity offers one more extremely valuable piece of information related to the messages that connected users exchange, mention or are exposed to. Such large datasets are quantitatively analyzed here based on methods used in content analysis, exposing valuable information on the interest of the general public (potential airliners users) of anomalies in the airline industry. The analysis is based on data from two real events (airliners’ crashes), which attracted the international public interest and significantly affected air travel demand. Finally, the results are analyzed and presented in detail such as to contribute to the air demand treatment, especially in terms of optimal communication operational management in cases of crises.     

多式联运数据交换区块链技术应用研究

针对多式联运数据交换中存在的数据中心化、作业协同效率不高等问题,对铁水联运、公铁联运过程中数据交换需求进行分析,阐述多式联运和区块链技术在数据共享、信任机制、安全机制和合约机制等方面的契合点,提出基于区块链的包括基础层、区块链核心层、应用服务层、应用接口和业务层的总体架构方案,设计基于联盟链的网络架构方式,模拟基于区块链技术的铁水联运运单流转过程,以实现共享数据的去中心化,提高多式联运作业的协同性和安全可靠性,促进多式联运"一单制"建设。     

Is the Mexico City metro an inferior good?

Time series cointegration techniques are used to estimate whether the Mexico City metro is perceived as a normal or inferior good. Owing to the fact that the Mexico City metro mainly serves the low income sectors of the population, this paper attempts to separate the overall income effect into two uncorrelated components: a vehicle stock effect (used as a proxy for medium/high income) and minimum wage effect net of the influence of vehicle stock (used as a proxy for low income). The time series cointegration results show that minimum wage elasticities are positive whilst vehicle stock elasticities are negative. These results suggest that for the majority of metro users, whose salaries are based on low multiples of the minimum wage and are not potential car owners, the Mexico City metro is perceived as a normal good. However, for middle/high income earners, who can afford to buy a private vehicle when their incomes increase, the Mexico City metro is perceived as an inferior good.     

Demand-responsive transit circulator service network design

Commuter rail systems are being introduced into many urban areas as an alternative mode to automobiles for commuting trips. It is anticipated that the shift from the auto mode to rail mode can greatly help alleviate traffic congestion in urban road networks. However, the right-of-way of many existing commuter rail systems is usually not ideally located. Since the locations of rail systems were typically chosen long ago to serve the needs of freight customers, the majority of current commuter rail passengers have to take a non-walkable connecting trip to reach their final destinations after departing the most conveniently located rail stations. To make rail a more viable commuting option and thus more competitive to the auto mode, a bus feeder or circulator system is proposed for transporting passengers from their departing rail stations to final work destinations in a seamless transfer manner. The key research question with operating such a bus circulator system is how to optimally determine a bus route and stopping sequence for each circulating tour by using the real-time demand information. In this paper, we name this joint routing and stopping optimization problem the circulator service network design problem, the objective of which is to minimize the total tour cost incurred to bus passengers and operators with respect to minimizing the walk time of each individual bus passenger. A bi-level nonlinear mixed integer programming model is constructed and a tabu search method with different local search strategies and neighborhood evaluation methods is then developed for tackling the circulator service network design problem.     

A combinatorial benders’ cuts algorithm for the quayside operation problem at container terminals

The quayside operation problem is one of the key components in the management system for a container terminal. In this paper, the integrated models proposed in the previous studies to address the quayside operation problem are examined and one of the potential frameworks is identified. A new method called combinatorial benders’ cuts algorithm is developed to solve the berth-level model in the framework. The computational experiment conducted in this research shows that the proposed approach is more efficient than the branch and cut algorithm embedded in CPLEX.     

Freight transport network design using particle swarm optimisation in supply chain–transport supernetwork equilibrium

This paper presents a discrete network design problem for optimally designing freight transport network in terms of the efficiency of supply chain. Modelling is undertaken within the framework of mathematical programmes with equilibrium constraints, which first incorporates both supply chain and transport networks explicitly. The upper level determines the best set of actions for transport network improvement, while the lower-level decision is based on a supply chain–multimodal transport supernetwork equilibrium. New variants of particle swarm optimisation are developed to approximately solve the upper level. Numerical tests reveal their superior performance and the effective freight transport-related actions.     

An analysis of an airport–airline relationship under a risk sharing contract

This paper analyzes a risk sharing incomplete contract under which an airline agrees to serve an airport in exchange for payment to/from the airport based on the difference between a realized and a target load factor. The key results are that we specified the relevant conditions on payments and utilities under which the incomplete contract can overcome the under-effort problem and achieve the efficient utility levels. These results are numerically illustrated by showing the impacts of the project prospect deterioration and the uncertainty increases on effort and utility levels.     

US airport financial reform and its implications for airport efficiency: An exploratory investigation

This study investigates the effect on airport productive efficiency of two major funding sources used by US airports, namely the Airport Improvement Program (AIP) grants and the Passenger Facility Charges (PFC). A two-stage Data Envelopment Analysis (DEA) modeling approach is employed for this purpose. In the first stage, we estimate airport productive efficiency using a variable returns-to-scale DEA model with both desirable and undesirable outputs. In the second stage, random effects regression models are estimated with airport efficiency scores from the first stage as the dependent variable and PFC and a proxy for AIP grants as two of the explanatory variables. By applying the two-stage DEA model to 42 primary US airports, it is found that PFC use has a positive impact on airport productive efficiency, whereas the impact of AIP grants is negative. Multiple counterfactual scenarios are examined by altering the mix of the two types of funding sources. The results show that simultaneously raising the PFC ceiling and decreasing AIP grants could lead to greater airport productive efficiency. The US federal aviation authority would also benefit from realizing these scenarios, especially given the budgetary constraints it faces.     

基于CIM模型的SCADA系统实时数据库

随着铁路牵引供电系统的发展,管理系统中各种异构系统不断涌现,为实现这些系统间的信息交换和互操作,方便第三方软件的接入,不同的系统间需构建一个开放的电力系统信息模型,IEC61970标准的CIM模型能很好地解决这一问题。针对构造符合CIM标准的SCADA内存数据库,提出在内存中组织基于符合IEC61970标准的数据库的设计及关键技术。     

A less-than-truckload carrier collaboration planning problem under dynamic capacities

This paper addresses the deterministic dynamic single carrier collaboration problem for the small- to medium-sized less-than-truckload (LTL) industry. It is formulated as a binary (0–1) multi-commodity minimum cost flow problem and solved using a branch-and-cut algorithm. Its inherent network structure is exploited to generate the lower bounds to the branch-and-cut algorithm using the network simplex method and by relaxing the integrality constraints. Results from numerical experiments indicate inherent trade-offs at the higher degrees of collaboration between waiting for more affordable collaborative capacity and incurring higher holding costs. They also suggest that collaborating LTL carriers experience increased capacity utilization.     

Flight and passenger efficiency-fairness trade-off for ATFM delay assignment

This paper studies trade-offs between efficiency (performance) and fairness (equity), when assigning ATFM delay pre-tactically (on-ground at origin airport) due to reduced airport capacity at destination. Delay is assigned as the result of the optimisation of a deterministic multi-objective problem considering flight and passenger perspectives when defining objectives of performance and fairness. Two optimisation cases are presented: one where objectives are based on flight metrics, and another one where they are based on passenger metrics. The paper defines and analyses efficiency-fairness trade-offs: the concepts of price of fairness for flights and passengers are defined as the percentage of efficiency loss due to the consideration in the optimisation of fairness; whereas the price of efficiency is considered as the fairness loss relative to the maximum value of the fairness metric, when considering flight or passenger delay in the optimisation. The optimisation model is based on the ground holding problem and uses various objective functions. For performance, total delay for flights (considering reactionary delay), and total delay for passengers (considering outbound connections) are defined. For fairness, the deviation of flight arrivals from a Ration By Schedule solution, and the deviation of delay experienced by passengers with respect to the one obtained in an RBS situation are used. An illustrative application on traffic at Paris Charles de Gaulle airport, a busy European hub airport, and including realistic values of traffic is modelled. A comprehensive trade-off analysis is presented. Results show, how in some cases, gains on one stakeholder can be achieved without implying any detriment on the other one. Passengers are more sensitive to the optimisation and hence, their consideration when assigning delay is recommended. Further research should explore how to combine flight and passenger indicators in the optimisation and consider how the lack of data availability could be mitigated.     

Meeting the on‐line needs of disabled tourists: an assessment of UK‐based hotel websites

The easy exchange of rich information between often geographically dispersed parties is an important precursor of successful tourism transactions. Internet‐based technologies, in particular the World Wide Web, offer possibilities to both buyers and sellers to exchange information without the constraints of geography and time diminishing its richness. The disabled, representing a significant part of any marketplace, may, however, have difficulties accessing the content of the Web and therefore sharing the benefits of rich information exchange. This is the principal concern of ‘Web content accessibility’. Focusing on the tourism sector, in particular UK‐based hotels, this paper examines the accessibility of their websites. However, recognising that it is not just access to information that is important for the disabled, but also the quality of that information, the paper also examines the extent to which the information contained on websites serves their particular needs. Utilising the accessibility testing software ‘Bobby’, disappointingly low levels of Web content accessibility were found amongst the sample of websites. Against a framework of information needs developed from criteria provided by disability organisations, the sample also revealed disappointingly low levels of specific (relevant) information for the disabled. Copyright © 2006 John Wiley & Sons, Ltd.     

Solutions to the request reassignment problem in collaborative carrier networks

The paper considers an arrangement for exchanging transportation requests to facilitate collaboration among independent carriers. The goal is to maximize the total profit without decreasing the individual profit of the carriers. Two solution approaches are developed for this problem involving decentralized control and auction based exchange mechanisms. The results are compared with those obtained without collaboration and by a centralized control. They indicate that horizontal collaboration pays off even in highly competitive environments.     

Ant colony optimization for disaster relief operations

This paper presents a meta-heuristic of ant colony optimization (ACO) for solving the logistics problem arising in disaster relief activities. The logistics planning involves dispatching commodities to distribution centers in the affected areas and evacuating the wounded people to medical centers. The proposed method decomposes the original emergency logistics problem into two phases of decision making, i.e., the vehicle route construction, and the multi-commodity dispatch. The sub-problems are solved in an iterative manner. The first phase builds stochastic vehicle paths under the guidance of pheromone trails while a network flow based solver is developed in the second phase for the assignment between different types of vehicle flows and commodities. The performance of the algorithm is tested on a number of randomly generated networks and the results indicate that this algorithm performs well in terms of solution quality and run time.     

Managing turnaround performance through Collaborative Decision Making

The purpose of this paper is to explore turnaround performance as a resultant from both Collaborative Decision Making (CDM) processes and collaborative measures. This paper presents how CDM operates in the Turnaround Process (TAP) to propose a new method for managing the collaborative turnaround performance of all actors by predicting the most critical indicators. To achieve this, data from a CDM airport is used. Sample data of 6500 observations, taken from turnaround movements handled in 2014 at Madrid-Barajas Airport, were obtained from three separate databases and analyzed separately (in three databases). To predict turnaround performance, this paper also introduces a predictor dependent variable called “star values” as a measure of minimal delay conditions in order to predict time performance. The analysis shows that the proposed method unveils a new approach in determining how collaborative performance can be measured in the TAP and the predicted key performance indicators, which shows variations in the predicted CDM indicators. Results challenge managers and policymakers to find which improvements can be enacted for better usage of airport infrastructures and resources for optimum use as well as enhanced TAP. In terms of theory use and extension, the study reveals how CDM is an essential element in the literature on air traffic management.     

Are measures of air-misses a useful guide to air transport safety policy?

Finding a proxy for analyzing and developing policy responses to rare events is often challenging. In the case of commercial airline accidents, these are small in number, especially within most national jurisdiction. This makes it difficult to use standard, objective probability techniques for assessing the impacts of various safety policies or for developing monetary measures for their inclusion in cost-benefit analysis studies. What is often used in place of the actual or predicted accident rate is a measure of ‘air’ (or ‘near’) misses that reflects the number of times a technically determined safety parameter is violated. The paper looks at whether this is a useful measure in terms of the quality of the data available, and whether it acts as a reasonable proxy when used in air transportation safety analysis and policy-making.     

Market- and non-market-based approaches to traffic-related pollution: the perception of key stakeholders

Market-based instruments have long been advocated on efficiency and welfare grounds, particularly by academics as a means of dealing with congestion and traffic-related pollution in urban areas. This paper details a survey of key UK stakeholders, namely local politicians, local transport officials and UK transport academics undertaken in order to ascertain their opinions with respect to a range of market- and non-market-based approaches aimed at dealing with the effects of road traffic in urban areas of the UK. The findings deal with how effective the key stakeholders perceive various market- and non-market based approaches to be as part of a package of measures, in dealing with the problem. The paper also details opinion with respect to acceptance of such measures and highlights areas of commonality between effectiveness and the acceptance of these measures. Finally, the paper draws a number of conclusions.     

铁路编组站阶段计划动态调整方法研究

铁路编组站阶段计划执行过程中的不确定事件导致其无法持续最优,阶段计划动态调整方法对于提高编组站作业效率具有重要意义。研究提出包括时间预测、动态车流推算、计划调整、计划实施、实时信息采集反馈等步骤的阶段计划动态调整流程,通过计算残差相关系数进行数据属性相关性分析和降维处理,利用机器学习方法和神经网络模型预测各阶段作业过程用时,建立基于作业过程用时精准预测的动态车流推算模型,对动态车流推算过程进行符号化描述,提出模型的约束条件和目标函数,设计基于蚁群算法的编组站动态车流推算模型求解算法。结果表明,作业过程用时预测误差随训练集样本数量增大而逐渐减小,蚁群算法计算时间满足阶段计划动态调整实际应用的需要。