Integrated operations planning and revenue management for rail freight transportation

In the rail industry, profit maximization relies heavily on the integration of logistics activities with an improved management of revenues. The operational policies chosen by the carrier have an important impact on the network yield and thus on global profitability. This paper bridges the gap between railroad operations planning and revenue management. We propose a new bilevel mathematical formulation which encompasses pricing decisions and network planning policies such as car blocking and routing as well as train make-up and scheduling. An exact solution approach based on a mixed integer formulation adapted to the problem structure is presented, and computational results are reported on randomly generated instances.     

公路隧道营运安全分析及对策

文章对公路隧道营运的特点及营运中存在的安全隐患作了介绍,并分析了事故的原因,最后提出相应的对策.     

Dynamics of highway design for safety

An important aspect of improving highway safety lies in designing the geometric features of roadways in response to the characteristics and behavior of drivers. This is being applied to specific features of highways with evidence of improvement in operation and safety. However, much more can be accomplished. There is now available additional operational experience and observations, which can assist the driver's task in vehicle control and guidance, but which have not yet been fully reflected in design criteria. If judiciously applied, such measures could further enhance highway safety. The paper addresses itself mainly to this aspect and presents the thesis: when all known or accepted safety features and techniques are applied fully to a highway project, it may be expected that a significant improvement in safety will be achieved. An actual project is suggested to validate this approach.     

A stochastic model for highway traffic

A nonlinear model for unidirectional flow of heavy traffic on a two-lane highway is considered. Features such as entrance, exit and lane transfer with time-dependent parameters are incorporated into the model, with the result that a number of previous models employed in the study of traffic flow become special cases of ours. Using the method of system-size expansion, an asymptotic analysis of the problem, including the time evolution of both deterministic and stochastic aspects of the traffic system, is carried out. In addition, a scheme for obtaining the moments of the probability distribution for systems of finite size is developed and a comparison is made with the exact results appropriate to a particular model. The agreement between the two sets of results turns out to be remarkably good.     

On user charges for highway financing

At both the federal and state levels, the main source of highway infrastructure financing has been from road-user charges, particularly in the form of fuel taxes. Although there are widespread differences from state to state in highway user charge structures, the formof these structures, in most states, has remained basically unchanged ever since such charges were introduced several decades ago. Changes in vehicle characteristics and usage, economic changes and concernsof energy conservation, and environmental protection have made an impact on the methods of user charges that have been traditionally used. This paper surveys current practices of user charges in the U.S. and reviews their appropriateness in the light of the changes that have occured and would continue to occur in the next decade or even in the next century. A possible future policy direction on highway user charge structure that can incorporate the technological and other emerging developments is then examined.     

Energy policies for passenger motor vehicles

This paper assesses the costs and effectiveness of several energy policies for light-duty motor vehicles in the United States, using a version of the National Energy Modeling System. The policies addressed are higher fuel taxes, tighter vehicle efficiency standards, and financial subsidies and penalties for the purchase of high- and low-efficiency vehicles (feebates). I find that tightening fuel-efficiency standards beyond those currently mandated through 2016, or imposing feebates designed to accomplish similar changes, can achieve by 2030 reductions in energy use by all light-duty passenger vehicles of 7.1–8.4%. A stronger feebate policy has somewhat greater effects, but at a significantly higher unit cost. High fuel taxes, on the order of $2.00 per gallon (2007$), have somewhat greater effects, arguably more favorable cost-effectiveness ratios, and produce their effects much more quickly because they affect the usage rate of both new and used vehicles. Policy costs vary greatly with assumptions about the reason for the apparent myopia commonly observed in consumer demand for fuel efficiency, and with the inclusion or exclusion of ancillary costs of congestion, local air pollution, and accidents.     

Strategies for managing highway transportation professional needs

Growth in highway spending and the loss of approximately one-third of the nation's professional engineers in state highway agencies will create significant problems and opportunities over the next decade. Careers in transportation will be attractive, rewarding and interesting, with promise for growing responsibility and advancement. This paper describes the dimensions of the problem and suggests approaches that should result in dynamic future-oriented organizations. Recruitment, education and training, compensation, professional satisfaction, skill requirements and other aspects of human resources management must be carefully matched to meet changing needs and skill requirements.     

农村公路的建设与设计

通过农村公路建设原则,提出了农村公路网建设要重实用、重排水、重防护的设计要点。     

An adaptive model for highway travel time prediction

Traffic congestion caused by either insufficient road capacity or unexpected events has been a major problem in urban transportation networks. To disseminate accurate traveler information and reduce congestion impact, it is desirable to develop an adaptive model to predict travel time. The proposed model is practically implementable to capture dynamic traffic patterns under various conditions, which integrates the features of exponential smoothing and the Kalman filter by utilizing both real‐time and historic data. The model is simple in formulation while robust in performance in terms of accuracy and stability. With a constraint or nonconstraint smoothing factor, the proposed model is tested with both real world and simulated data and demonstrated itself a sound model that outperforms others (e.g., Kalman filter and simple exponential smoothing) specifically under recurring and nonrecurring congestion. Copyright © 2012 John Wiley & Sons, Ltd.     

公路隧道通风设计软件(VDSHT)的编制及特点

通风技术是21世纪公路隧道发展的关键技术之一,但目前国内的通风计算仍以手工为主,工作效率较低,不便于多方案的评价比选.文章介绍了一套隧道通风设计软件(VDSHT)[2],它不仅可以进行各种纵向、半横向、全横向和混合通风方式的计算,而且可以进行多种通风方案的评价比选.     

夹活岩特长公路隧道通风方案研究

夹活岩特长公路隧道位于沪蓉国道主干线湖北省宜昌至恩施高速公路上,长约5 200m.文章通过对隧道运营通风系统各比选方案进行计算、分析,确定技术可靠、经济相对较省的运营通风方式,期望能对以后的公路隧道通风工程建设有所借鉴.     

公路机电项目技术规范编制的探讨

本文结合多年机电工程管理,探讨了高速公路机电工程项目的技术规范编制工作。高速公路机电工程项目技术规范是机电工程建设前期工作的重点和难点,作为工程施工建设的依据,在后续的工程建设中的起到关键作用。     

Pareto-improving congestion pricing and revenue refunding with multiple user classes

This study investigates Pareto-improving congestion pricing and revenue refunding schemes in general transportation networks, which make every road user better off as compared with the situation without congestion pricing. We consider user heterogeneity in value of time (VOT) by adopting a multiclass user model with fixed origin–destination (OD) demands. We first prove that an OD and class-based Pareto-improving refunding scheme exists if and only if the total system monetary travel disutility is reduced. In view of the practical difficulty in identifying individual user’s VOT, we further investigate class-anonymous refunding schemes that give the same amount of refund to all user classes traveling between the same OD pair regardless of their VOTs. We establish a sufficient condition for the existence of such OD-specific but class-anonymous Pareto-improving refunding schemes, which needs information only on the average toll paid and average travel time for trips between each OD pair.     

Advanced pricing and rationing policies for large scale multimodal networks

The applying of simplified schemes, such as cordon pricing, as second-best solution to the toll network design problem is investigated here in the context of multiclass traffic assignment on multimodal networks. To this end a suitable equilibrium model has been developed, together with an efficient algorithm capable of simulating large scale networks in quite reasonable computer time. This model implements the theoretical framework proposed in a previous work on the toll optimization problem, where the validity of marginal cost pricing for the context at hand is stated. Application of the model to the real case of Rome shows us, not only that on multimodal networks a relevant share (up to 20%) of the maximum improvements in terms of social welfare achievable with marginal cost pricing can in fact be obtained through cordon pricing, but also that in practical terms rationing is a valid alternative to pricing, thus getting around some of the relevant questions (theoretical, technical, social) the latter raises. As a result we propose a practical method to analyze advanced pricing and rationing policies differentiated for user categories, which enables us to compare alternative operative solutions with an upper bound on social welfare based on a solid theoretical background.     

Impact of pricing and transit disruptions on bikeshare ridership and revenue

Transportation - Bikeshare operators routinely explore options to improve ridership and revenue by studying interaction among pricing, service and operations. The objective of this research is to...     

黄土公路隧道围岩压力测试分析

隧道围岩压力是一个极其复杂的问题,涉及的因素较多.论文论述了利用现场测试手段对两座黄土隧道进行的测试结果,分析了围岩压力的大小和分布形式,并和已有的计算结果进行了分析对比,对浅埋和深埋的界定标准以及二次衬砌和仰拱问题也作了论述.     

Transportation funding structures and policies

The transportation enterprise in the United States relies heavily on federal funding of highways, transit, and airports. Consideration of changes in federal funding policies over the past decade or so, and the effects of those policies, suggests that the way programs are financially structured can be critically important. The present analysis leads to recommendations concerning the selection of the federal matching ratio, tradeoffs between categorical and block programs, and the use of formula or discretionary allocations. It highlights the importance of ascertaining programmatic intent in establishing funding policies, as well as the need for sensitivity to the fiscal climate.     

A linear programming-based method for the network revenue management problem of air cargo

One critical operational issue of air cargo operation faced by airlines is the control over the sales of their limited cargo space. Since American Airlines’ successful implementation in the post-deregulation era, revenue management (RM) has become a common practice for the airline industry. However, unlike the air passenger operation supported by well-developed RM systems with advanced decision models, the decision process in selling air cargo space to freight forwarders is usually based on experience, without much support from optimization techniques. This study first formulates a multi-dimensional dynamic programming (DP) model to present a network RM problem for air cargo. In order to overcome the computational challenge, this study develops two linear programming (LP) based models to provide the decision support operationally suitable for airlines. In addition, this study further introduces a dynamic adjustment factor to alleviate the inaccuracy problem of the static LP models in estimating resource opportunity cost. Finally, a numerical experiment is performed to validate the applicability of the developed model and solution algorithm to the real-world problems.     

Discrete and continuous models for computation of optimal vertical highway alignment

This paper describes a dynamic programming model and a state parametrization model formulated to solve two-dimensional highway location problems. A numerical example is presented to compare the solutions obtained using the two models. Features of the two approaches, with respect to their applicability in solving three-dimensional highway location problems in particular, are highlighted. This study forms the basis of a three-dimensional model that computes optimal horizontal and vertical alignments simultaneously.