Existence and efficiency of oligopoly equilibrium under toll and capacity competition

This paper studies the existence and efficiency of oligopoly equilibrium under simultaneous toll and capacity competition in a parallel-link network subject to congestion. We establish sufficient conditions for the existence of a pure-strategy oligopoly equilibrium and then derive upper bounds on the efficiency loss of the oligopoly equilibrium over the social optimum under different inverse demand function assumptions, respectively. Furthermore, we show that these bounds are demand-function free and only dependent upon the number of competitive roads.     

Reformulating Environmentally Constrained Traffic Equilibrium via a Smooth Gap Function

Various government laws have recently been enacted to alleviate the environmental deterioration of transportation systems. Environmental constraint is a valid means to explicitly reflect various environmental protection requirements imposed by the government. In this paper, we examine the environmentally constrained traffic equilibrium problem (EC-TEP), which is a fundamental tool for modeling and evaluating environmental protection requirements. Specifically, we provide an equivalent reformulation for the EC-TEP. The proposed reformulation adapts the concept of gap function to simultaneously reformulate the nonlinear complementarity conditions associated with the generalized user equilibrium conditions, environmental constraints, and conservation constraints as an equivalent unconstrained optimization problem. This gap function reformulation has two desirable features: (1) it can handle a general environmental constraint structure (linear or nonlinear; link-based or area-based) and a general link and route cost structure, enhancing the modeling adaptability and flexibility; (2) it is smooth and unconstrained, permitting a number of existing efficient algorithms for its solution. A gradient-based solution algorithm with a self-regulated averaging stepsize scheme is customized to solve the reformulated unconstrained optimization problem. Numerical examples are also provided to demonstrate the modeling flexibility of the proposed EC-TEP reformulation.     

Tradable travel credits for congestion management with heterogeneous users

This paper carries on the recent work of Yang and Wang (2011) on tradable credit schemes by considering heterogeneous users with different value of time (VOT). Given a tradable credit scheme, the user equilibrium (UE) and market equilibrium (ME) conditions with heterogeneous users are formulated into a variational inequalities (VI) problem. Sufficient conditions for uniqueness of the aggregate UE link flows and then the ME credit price are established. Appropriate tradable credit schemes are developed to decentralize system optimal and Pareto-improving network flow patterns. Extension is made to the elastic demand case.     

Decentralizing Pareto-efficient network flow/speed patterns with hybrid schemes of speed limit and road pricing

This paper examines the potential of hybrid schemes of speed limit and road pricing for decentralizing Pareto-efficient flow/speed patterns that minimize total travel time and total emissions simultaneously. Both link flows and speeds are treated as independent variables in our bi-objective formulation. The resulting Pareto frontier is thus weakly dominant to that in previous literature. For any such favorable Pareto-efficient flow and speed pattern, we establish the existence of hybrid schemes of speed limits and non-negative/revenue-neutral tolls, whose set of user equilibrium (UE) solutions contains the Pareto-efficient one, and provide sufficient conditions under which the Pareto-efficient solution can be certainly obtained.     

Joint implementation of tradable credit and road pricing in public-private partnership networks considering mixed equilibrium behaviors

This paper investigates joint road charging schemes in a public-private partnership (PPP) network by simultaneously taking into account Cournot-Nash (CN) players and user equilibrium (UE) players. Each joint scheme comprises a tradable credit plan for public roads and a regular tolling plan for private roads. We show that, under UE-CN mixed equilibrium, there exist anonymous nonnegative joint schemes that can support a system optimum link flow pattern. By using preemptive approach, we further design three bi-objective optimization models with hybrid implementation of tradable credit and road pricing. Numerical examples demonstrate that the proposed methods are effective in managing PPP networks.     

The equilibrium of closed-loop supply chain supernetwork with time-dependent parameters

In this paper, we develop a closed-loop supply chain supernetwork model including suppliers, manufacturers, retailers and consumers at demand market, in which the demand for product is seasonal (t), and the sensitivity (w) of demand to price is another key factor which effects consumers’ demand. Moreover, the manufacturers invest the reverse distribution channel for incenting consumers to return more used products. Based on the Evolutionary Variational Inequalities (EVI) theory and Projected Dynamical Systems (PDS), the equilibrium condition of closed-loop supply chain is formulated, and the model is verified reasonably by numerical example.     

An origin–destination based road pricing model for static and multi-period traffic assignment problems

To mitigate traffic externalities, we propose an origin–destination (OD) based road pricing model for traffic assignment problems. For elastic demand, we derive explicit optimal tolls for the OD-based pricing scheme. We also extend the model to a multi-period static traffic assignment (MSTA) where we derive analytically the route and OD-dependent tolls based on equilibrium conditions. We present some examples to show that the OD-based tolling scheme could improve the system welfare significantly, compared to the no-toll scenario (user equilibrium – UE).     

Braess Paradox of traffic networks with mixed equilibrium behaviors

Under the user equilibrium (UE) behavior assumption, the Braess Paradox (BP) and its variations have been well investigated. However, users do not always follow the UE behavior. In reality, there are likely quiet a few non-collaborative Cournot–Nash (CN) players coexisting with UE players in the common traffic network. Users in a CN player are completely collaborative to minimize their total travel cost and users subordinating to different players are perfectly competitive. Considering both UE and CN players in the congested network, it remains unclear that under what conditions the BP will occur. In this paper, the BP occurrence conditions under the UE–CN mixed equilibrium are firstly investigated using the classical Braess network with linear link cost function. Then, the BP conditions are studied to the ordinary grid network with nonlinear link cost function. It is shown that the BP occurrence in the conventional Braess network depends upon the link travel time function parameters and the demand level of users controlled by UE/CN players, and the BP occurs in the grid network only for certain demand combinations of users under one UE player and two CN players.     

Tradable credit scheme for mobility management considering travelers’ loss aversion

Under a given tradable credit scheme, travelers’ loss aversion behavior for credit charging during the route choice process is studied. A disutility function of loss aversion is applied to approach travelers’ different attitudes towards credit loss and gain, and the transaction costs of buying and selling credits are also incorporated in the function. The user equilibrium (UE) and market equilibrium (ME) conditions considering loss aversion effects are formulated into a variational inequality (VI) problem. Analyses demonstrate that the system optimum (SO) credit scheme does not always exist. A proposition is further presented to guarantee its existence.     

在开行直达列车线路上组织五定班列的研究

根据铁路定点、定车次、定线、定时、定价货运班列的开行情况,分析在开行直达列车线路上组织五定班列的必要和充分条件。由每周货物平均发送量和列车牵引质量计算出开行列数,根据有关规则以每周至少开行1列为必要条件。考虑运费和货物提前到达产生的经济效益,以开行五定班列比开行直达列车的经济效益大为充分条件。对各参数选择的影响进行分析并给出算例应用。     

Towards a theory of decoupling: degrees of decoupling in the EU and the case of road traffic in Finland between 1970 and 2001

Traditionally, the transport literature reflects the view that traffic volumes, road traffic volumes in particular, are coupled with Gross Domestic Product (GDP). Recently published literature also argues that the carbon dioxide (CO₂) emissions from transport, passenger cars in particular, have not shown any decoupling from transport volumes for some years. This article presents a theoretical framework for decoupling, defining the difference between decoupling, coupling and negative decoupling. These are further broken down to weak, strong and expansive/recessive degrees of decoupling, laying emphasis on the absolute increase or decrease of the variables. The result section presents data of the development of the relationships between GDP, traffic volumes and CO₂ emissions from transport in the EU15 countries between 1970 and 2001, including the special case of Finnish road traffic. The aggregate EU15 data show a change from expansive negative decoupling to expansive coupling regarding passenger transport, and from weak decoupling to expansive negative decoupling regarding freight transport. Weak decoupling of transport CO₂ emissions from GDP could also be observed. Weak decoupling of all the three aspects (freight, passenger and CO₂) could be seen in the UK, Sweden and Finland in the 1990s. In Finland, the statistics show weak decoupling of GDP from road traffic volume and strong decoupling of road traffic volume and CO₂ emissions from road traffic between 1990 and 2001. Four hypothetical explanations of the Finnish phenomenon are put forward in this article: policy towards sustainable mobility, green urban lifestyle, increasing income differences, and statistical misinterpretation. Each explanation is backed up with some quantitative evidence in observable trends in Finland during the 1990s.     

用户平衡配流条件下易腐货物运输损耗研究

易腐货物的运输损耗量是交通时间的函数,确定交通时间对于运输损耗的计算尤为重要。以易腐货物为研究对象,建立双层规划模型,上层为易腐货物运输损耗模型,下层为用户平衡配流模型。当路径中车流形成用户平衡配流状态时,用凸组合法对模型进行求解。并通过算例说明模型的计算和应用。     

Time-geographic relationships between vector fields of activity patterns and transport systems

The rise of urban Big Data has made it possible to use demand data at an operational level, which is necessary to directly measure the economic welfare of operational strategies and events. GIS is the primary visualization tool in this regard, but most current methods are based on scalar objects that lack directionality and rate of change – key attributes of travel. The few studies that do consider field-based time geography have largely looked at vector fields for individuals, not populations. A population-based vector field is proposed for visualizing time-geographic demand momentum. The field is estimated using a vector kernel density generated from observed trajectories of a sample population. By representing transport systems as vector fields that share the same time–space domain, demand can be projected onto the systems to visualize relationships between them. This visualization tool offers a powerful approach to visually correlate changes in the systems with changes in demand, as demonstrated in a case study of the Greater Toronto Area using data from the 2006 and 2011 Transportation Tomorrow Surveys. As a result, it is now possible to measure in real time the effects of disasters on the economic welfare of a population, or quantify the effects of operational strategies and designs on the behavioural activity patterns of the population.     

Evolutionary variational inequalities and applications to complex dynamic multi-level models

In this paper we consider a supply chain network model with three tiers of decision-makers (manufacturers, retailers, and consumers) in the case when prices and shipments are evolving on time. Moreover, we assume that excesses of production and excesses of demand of the commodity are present. For such a framework we furnish, using the infinite dimensional duality theory, the equilibrium conditions for the representatives of each tier of the supernetwork, the time-dependent variational formulation governing the complete supply chain supernetwork, and we provide some existence theorems and a numerical example.     

A threshold covering flow-based location model to build a critical mass of alternative-fuel stations

To facilitate the transition to alternative-fuel vehicles (AFVs), researchers have developed models for optimally locating an initial refueling infrastructure for AFVs with limited driving range. Recently, clustering of stations has emerged as a strategy to encourage consumers to purchase AFVs by building a critical mass of stations. Clustering approaches, however, have focused on serving demands represented as nodes or arcs rather than origin-destination (O-D) trips. This study proposes a Threshold Coverage extension to the original Flow Refueling Location Model that focuses on the percentage of a zone's O-D trips that can be successfully completed given a typical driving range and location of stations. It is motivated by the idea that drivers in an area will not purchase an AFV unless a critical mass of the trips they regularly make can be completed. Therefore, the new model optimally locates p refueling stations on a network to maximize the sum of weighted demand of covered origin zones, where “covered” means that the zone exceeds a specified threshold percentage of their total outbound round trips that are refuelable. The model is tested on networks for Orlando and the state of Florida. As the threshold percentage is raised, fewer zones can surpass the threshold. Covered nodes increasingly cluster together, as do stations for serving their O-D flows. The model's policy implementation will provide managerial insights for some key concerns of the industry, such as geographic equity vs. critical mass, from a new perspective.     

A tale of airline competition: When full-service carriers undercut low-cost carriers fares

The pricing of low-cost carriers (LCCs) compared with traditional airlines has been extensively investigated since their inception in the air transport market. Abundant empirical evidence attests that, on average, LCCs' fares (per km) are lower than those usually offered by full-service carriers (FSCs). Such literature, however, paid virtually no attention to the conditions under which LCCs lose their convenience compared to traditional airlines. The purpose of this study is to investigate the occurrence of LCCs sometimes offering higher fares than FSCs on competing flights. By using a dataset expressly collected for this purpose, we are able to quantify its frequency and suggest some possible explanations. These findings concur to cast some questions on the widely held preconception of vertical differentiation between LCCs' and FSCs’ offered services. Further research will be needed in order to understand the relative weight of the suggested factors.     

拥挤条件下的铁路随机用户平衡配流模型

在对铁路客流分配问题进行概述的基础上,结合铁路旅客运输组织的特点,采用平衡分配法对铁路客流分配问题进行研究,建立了拥挤条件下的铁路随机用户平衡配流模型,并给出了求解算法和算例。     

A dynamic demand analysis of the United States air-passenger service

This study examines the short- and long-run effects of various determinants on the demand for US air passenger-services using the Johansen cointegration analysis and a vector error-correction (VEC) model. Results show that, in the long-run, airfare, disposable income and NASDAQ have significant effects on US air travel demand. The combined short-run dynamic effects of disposable income, NASDAQ, population and airfare jointly explain changes in air passenger-miles. Finally, we find that the 9/11 terrorist attacks drop air passenger demand by 5% during 2001:Q3-2002:Q2, which in turn pushes down the seat capacity by 4%. However, it has little impact on airfare.     

铁路旅客列车车底套用优化模型的研究

在列车车底数量有限的条件下,利用多商品网络流模型对列车车底的套用问题建立数学优化模型,对车底套用方案进行优化,即把列车运行图转化为网络图,而后根据流守恒、容量限制和维修等约束条件,建立以列车运输能力最大化为目标的整数规划模型。     

A methodology based on the Analytic Hierarchy Process for the quantitative assessment of emergency preparedness and response in road tunnels

The paper presents and discusses a methodology to judge the effectiveness of the preparedness activities in case of accidents in road tunnels by considering the system from several points of view (i.e. structural/technical, organizational/human, and contextual). Due to the different nature of the criteria involved in the assessment activity, we chose to apply the Analytic Hierarchy Process methodology (Saaty, T.L. (2006). Fundamentals of Decision Making and Priority Theory with the Analytic Hierarchy Process, RWS Publications, Pittsburgh) that allows comparing and appraising quantitatively variables that are incommensurable and that may originate from distinct and separate areas. The paper identifies the hierarchic structure necessary to measure both the performance of the emergency response system for road tunnel accidents and the weights for assessing their relative importance. Finally, the methodology is applied to a case study on a transnational road tunnel between Italy and France to show a feasible evaluation of the sensitivity of the structure to the input variables in order to find the most valuable enhancing and improving actions.