The multi-class, multi-criterion traffic equilibrium and the efficiency of congestion pricing

We consider the effect of the so-called second-best tolls on the price of anarchy of the traffic equilibrium problem where there are multiple classes of users with a discrete set of values of time. We derive several bounds of the price of anarchy for this problem when the tolls are considered and not considered as part of the system cost, with the time-based criterion and the cost-based criterion, respectively. All the bounds give us useful information on the effect of the tolls, which can be used to design network toll schemes.     

Making urban road pricing acceptable and effective: searching for quality and equity in urban mobility

Urban Road Pricing has been proposed many times as a powerful instrument to fight congestion in urban traffic, but has systematically faced a hostile political envirionment, due to lack of confidence on its promised (traffic) results and fear of its political consequences. Lack of action in this front is contributing to stable or even growing congestion problems in most large cities.This paper tries to address the problem with a fresh look at the objectives of road pricing and at the reasons for that political hostility. For managing and developing the urban mobility system, efficiency and equity are normally taken as the basic economic objectives. Sustainability objectives may be integrated in the efficiency objective if we are able to represent adequately the costs of the resources consumed in the process. Political hostility is normally based on having to pay for what was freely available, and on the risk of exclusion for those with little revenue available for the extra cost of driving into the city.Pursuit of efficency leads to suggestion of marginal social cost pricing but this is hard to explain to the public and application of this principle is fraught with pitfalls since some components of that cost get smaller as traffic grows (noise related costs for example). Pricing is still a good option but the objective has to be something easier to understand and to serve as a target for mobility managers. That “new” objective is quality of the mobility system, with a meaning similar to that of “level of service” in traffic engineering, and prices should be managed to across space, time and transport modes in such a way that provision of service is made with good quality in all components.Pursuit of equity leads to some form of rationing, which has often been associated with high transaction costs and abuse by the administrators. But the use of electronic road pricing should allow easy ways to address the rationing process without such high costs. The basic proposition is that all local taxpayers receive as a direct restitution of their tax contribution a certain amount of “mobility rights”, which can be used both for private car driving in the tolled areas and for riding public transport.These principles are easily applicable with a variety of technical solutions for road pricing, from the simplest cordon pricing to the more sophisticated “pay-as-you-go” schemes. The paper addresses this question of implementation and argues for increasingly sophisticated schemes, as people get accustomed to the principles and finer targeting of demand segments may be needed.     

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).     

Evolution of a dynamic ridesharing system based on rational behavior of users

A dynamic ridesharing system (DRS) is a system where users can find ridesharing partner(s) at any time, even shortly before making a trip. A DRS that does not consider individual preferences may cause dissatisfied matchings of users in a shared vehicle and lead to abandonment of DRS in the long term. To investigate the evolution of DRS, such as long-term adoption, this study develops a model of DRS considering the rational behavior and learning process of its users. User behavior is considered as travel mode choice and ridesharing partner choice decisions under the expected utility maximization concept. The day-to-day evolution of a DRS is simulated based on the proposed model, and the effects of user learning behaviors and some social factors pertinent to long-term DRS adoption are investigated.     

Achieving genuinely dynamic road user charging: issues with a GNSS-based approach

A variety of approaches to road user charging (RUC) for reducing congestion and raising revenue to maintain and improve transport infrastructure is in place in many countries; examples of such RUC include: an Electronic Fee Collection System in Singapore, Cordon Pricing in Oslo City in Norway, Zoned Based Pricing in London and Distance-Based Pricing (also called Pay-As-You-Drive) in Germany and Switzerland. With the development of satellite technologies, the introduction of dynamic pricing becomes possible, affording an opportunity for RUC to fully reflect the ‘Polluter Pays Principle’. This paper provides critical and comparative assessments of existing road user charging (RUC) systems with reference to technological limitations and public and political acceptability. The paper then goes on to demonstrate a system architecture for a Global Navigation Satellite System (GNSS) based dynamic road user charging system capable of considering dynamic variables. Finally we consider the feasibility of the proposed system in relation to technology readiness and public acceptability. We then consider some potential wider benefits from the introduction of a comprehensive system that could be highlighted to justify the cost of development and implementation as well as to improve public and political acceptability. The paper ends with conclusions and future research directions.     

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.     

Port economic cost functions: A service perspective

Ports provide services rather than producing physical products. However, port cost functions specify port cost as functions of physical products, e.g., port cargo throughput long-run cost is a function of port resource prices and cargo throughput (a physical product). In comparison, port cargo service long-run cost is a function of port resource prices, cargo service and shipper cargo received. The shipper provides cargo that is serviced by the port. A service cannot be touched and its user is involved in its provision. This paper derives port cost functions for which port outputs are “service outputs”, e.g., cargo, vessel and vehicle services.     

The fixed charge facility location problem with coverage restrictions

This paper develops a fixed charge facility location model with coverage restrictions, minimizing cost while maintaining an appropriate level of service, in identifying facility locations. Further, it discusses the insights that can be gained using the model. Two Lagrangian relaxation based heuristics are presented and tested. Both heuristics use a greedy adding algorithm to calculate upper bounds and subgradient optimization to calculate lower bounds. While both procedures are capable of generating good solutions, one is computationally superior.     

Development of level of service standards for airport facilities: Application to São Paulo International Airport

A methodology for developing level of service (LOS) standards at airport passenger terminals based on user perceptions is developed. The underlying concept is the derivation of quantitative values for passenger perceptions of service based on airport surveys. The check-in counter component is evaluated considering factors that have a bearing on the user perceptions of LOS: processing time, waiting time, and space available per person. The study uses data obtained from a passenger survey conducted at São Paulo/Guarulhos International Airport, Brazil. The results indicate that we can derive quantitative perception scales from qualitative survey data. Finally, a multi-attribute analysis is done to obtain a composite evaluation of LOS at the check-in counter as a function of the waiting time, processing time, and space available.     

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.     

A diagrammatic analysis of the market for cruising taxis

A diagrammatic approach is used to study the characteristics of the cruising taxi market. For cost modeling, both taxi operator and passenger are taken as service producers. The former provides his vehicle operation and the latter, his waiting and travel time. Market demand is defined as a function of generalized price. It is shown that under short and long run conditions a unique equilibrium exists for a deregulated industry and it corresponds to a monopolistic competition. The relations among the free market equilibrium, social optimum and second best solution are analyzed. Regulations are studied in order to find their social convenience.     

Air express network design based on express path choices – Chinese case study

Due to the shortage of cargo aircraft, Chinese express companies have to provide transportation services with a hybrid method that consists of “rented bellies and self-owned cargo aircraft”. Because the bellies are rented from air passenger companies and because the cargo aircraft are owned by the express companies, it is important for the express companies to use their cargo aircraft as effectively as possible. This paper constructs a bi-level model to optimize the flight transportation network of an express company. The upper model designs the network and allocates the transportation capacity with the objective of minimizing the total transportation cost, and the lower model calculates the link flows in user equilibrium. Data from ShunFeng (SF) Express Company (China) are used to conduct the case study. Using the model outputs, the flows on links and at nodes are analyzed to illustrate the transportation and transshipment situations.     

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.     

Exploring multiple eco-routing guidance strategies in a commuting corridor

The introduction of eco-routing systems has been suggested as a promising strategy to reduce carbon dioxide emissions and criteria pollutants. The objective of this study is to scrutinize the impacts of an eco-routing guidance system on emissions through the use of a case study in a commuting corridor. This research aims at assessing the potential environmental benefits in terms of different pollutant emissions. Simultaneously, it addresses the extent of variations in system travel time (S_TT) that each eco-routing strategy implies. The methodology consists of three distinct phases. The first phase corresponds to the adjustment of a microsimulation platform of traffic and emissions with empirical data previously collected. Second, to volume-emission-functions (VEF), developed based on the integrated modeling structure. Final, to different scenarios of traffic flow optimization performed at the network level based on a simplified assignment procedure. The results show that if the traffic assignment is performed with the objective to minimize overall impacts, then the total system environmental damage costs can be reduced up to 9% with marginal oscillations in total S_TT. However, if drivers are advised based on their own emissions minimization, total system emissions may be higher than under the standard user equilibrium flow pattern. Specifically, environmentally friendly navigation algorithms focused on individual goals may tend to divert traffic to roads with less capacity affecting the performance of the remaining traffic. This case study brings new insights about the difficulties and potentials of implementing such systems.     

车辆修理集中化布局的双层规划模型研究

在对车辆修理点布局问题分析的基础上,以规划期内修理点的改扩建费用、运营费用和运输费用之和最小为目标建立上层模型,以运输费用最小为目标建立下层模型,以此建立了车辆修理点布局的双层规划优化模型,并给出了相应的求解算法。模型具有较好的适用性和实用性,为铁路车辆修理点的进一步优化调整奠定了较好的理论基础。     

The generalized bin packing problem

In the Generalized Bin Packing Problem (GBPP), given two sets of compulsory and non-compulsory items characterized by volume and profit and a set of bins with given volume and cost, we want to select the subset of profitable non-compulsory items to be loaded together with the compulsory ones into the appropriate bins in order to minimize the total net cost. Lower and upper bounds to the GBPP are given. The results of extensive computational experiments show that the proposed procedures are efficient and the bounds are tight.     

The generalized bin packing problem

In the Generalized Bin Packing Problem (GBPP), given two sets of compulsory and non-compulsory items characterized by volume and profit and a set of bins with given volume and cost, we want to select the subset of profitable non-compulsory items to be loaded together with the compulsory ones into the appropriate bins in order to minimize the total net cost. Lower and upper bounds to the GBPP are given. The results of extensive computational experiments show that the proposed procedures are efficient and the bounds are tight.     

Bi-objective bilevel optimization of distribution center locations considering user equilibria

We propose a bi-objective, bilevel optimization model for the location of relief distribution centers (DCs) in humanitarian logistics. The upper-level decision-maker (an aid-providing organization) selects locations for capacitated DCs. On the lower level, beneficiaries choose a DC according to distance and amount of supply to be expected. This effects a user equilibrium on the lower decision level. Upper level objectives are to minimize total opening cost for the DCs and total uncovered demand. We develop an exact algorithm for determining the Pareto frontier of the problem, integrating the adaptive epsilon-constraint method, a branch-and-bound procedure, and the Frank–Wolfe procedure.     

Coordinated aviation network resource allocation under uncertainty

Congestion in the air traffic system, both recurrent and non-recurrent, is typically handled by rationing access rights to individual resources such as airports or important parts of the airspace. Under the planning paradigm employed in the US, this rationing process occurs independently at each resource. The stochastic integer programming model proposed in this paper brings coordination to this process while considering capacity uncertainty. Results of a case study suggest that the model is tractable, and generates capacity allocations that improve efficiency and enable greater responsiveness to changing capacity conditions.     

Tradable credit schemes for managing bottleneck congestion and modal split with heterogeneous users

This paper examines the efficiency of a tradable travel credit scheme for managing bottleneck congestion and modal split in a competitive highway/transit network with continuous heterogeneity in the individuals’ value of time. Each user is initially endowed with a certain amount of travel credits and can sell or buy additional credits in a free trading market. Time-dependent credit charge is implemented only for usage of the road bottleneck. We show that both the modal split and credit charge at equilibrium are unique, and the scheme is always Pareto-improving when the system optimum is achieved.