Asymptotically Optimal Algorithms for Pickup and Delivery Problems with Application to Large-Scale Transportation Systems

The Stacker Crane Problem is NP-Hard and the best known approximation algorithm only provides a 9/5 approximation ratio. The objective of this paper is threefold. First, by embedding the problem within a stochastic framework, we present a novel algorithm for the SCP that: (i) is asymptotically optimal, i.e., it produces, almost surely, a solution approaching the optimal one as the number of pickups/deliveries goes to infinity; and (ii) has computational complexity O(n^{2+\eps}), where $n$ is the number of pickup/delivery pairs and \eps is an arbitrarily small positive constant. Second, we asymptotically characterize the length of the optimal SCP tour. Finally, we study a dynamic version of the SCP, whereby pickup and delivery requests arrive according to a Poisson process, and which serves as a model for large-scale demand-responsive transport (DRT) systems. For such a dynamic counterpart of the SCP, we derive a necessary and sufficient condition for the existence of stable vehicle routing policies, which depends only on the workspace geometry, the stochastic distributions of pickup and delivery points, the arrival rate of requests, and the number of vehicles. Our results leverage a novel connection between the Euclidean Bipartite Matching Problem and the theory of random permutations, and, for the dynamic setting, exhibit novel features that are absent in traditional spatially-distributed queueing systems.Comment: 27 pages, plus Appendix, 7 figures, extended version of paper being submitted to IEEE Transactions of Automatic Contro

Planning and operation of transport systems in Mediterranean Mid-Size Metropolitan Areas: Lisbon and Homs as a case studies

Urban sustainability, economic performance and tourist attractiveness require a comprehensive and efficient functioning multimodal transport system. In recent centuries, the importance role of urban transport and its means were not a result of urban growth, since the inception of cities; it has been a major junction of the city. More efficient urban transport would allow cities to ensure better accessibility to the various services. At the same time, they should help reducing the transport externalities such as traffic congestion, road crashes and environmental pollution. In the 1995’s Barcelona Conference, where transport was identified as a priority issue, a broad consensus points out that transport reform should be an integral part of economic adjustment at the national level as well as intergovernmental cooperation at the regional level. The idea of this dissertation inspired by me as a student. Portugal is my first abroad country, I felt it as my second country, as it is a Mediterranean country as well as Syria. At the same time, I felt that my responsibility is to contribute to its development and improvement in all aspects, to have an organized and sustainable transport services, that ensures mobility and basic access to meet the needs of development without affecting the quality of life for subsequent generations. So, it must be safe, healthy, inexpensive and with less impacts regarding pollution and the use of renewable and non-renewable resources, it should meet the needs of the present without affecting or damaging the environmental harmony and the need to achieve a long-term sustainable economy and convenience for society. The objective of this research is to identify some specificities of cities in the Mediterranean region that can somehow explain the existing difficulties they show regarding the efficiency of their transport systems, the growing predominance of car use, the delay to improve active modes of transport, as well as the transport policy reforms, they are trying to implement. The similarities between Lisbon and Homs in this regard were used to better understand the problems that those cities face and what are the strategies to explore in order to reach a more efficient and sustainable transport system. In most of the southern Mediterranean countries transport reforms are now underway but does not have an identity yet comparing with the northern countries. However, I am taking Lisbon’s transport policies and urban mobility management as a case-study, to identify the policies and measures that can be applied in Homs, helping this city to plan more efficiently its transport system. As a result, an interaction exists between transport system and its use, as they influence each other. I’m focused in this dissertation on the user perspective. Methods were used that focus on the people and reveal his thoughts, knowledge, experience and feelings and how the world is going forward.A sustentabilidade urbana, o desempenho económico e a atratividade turística exigem um sistema de transportes multimodal, abrangente e eficiente. Nos últimos séculos a importância do papel do transporte urbano e dos seus meios não foram apenas o resultado do crescimento urbano, antes o influenciaram desde o início das cidades. Um transporte urbano mais eficiente permitirá às cidades garantir uma melhor acessibilidade aos vários serviços. Ao mesmo tempo, deve ajudar a reduzir as externalidades dos transportes, como congestionamentos, acidentes rodoviários e poluição ambiental. Na Conferência de Barcelona de 1995, onde o transporte foi identificado como uma questão prioritária, um amplo consenso apontou para que a reforma do transporte fosse parte integrante do desenvolvimento económico ao nível nacional, bem como exemplo da cooperação intergovernamental ao nível regional. A ideia desta dissertação inspirou-me como estudante. Portugal é o primeiro país estrangeiro em que vivi, senti-o como o meu segundo país, pois é um país mediterrâneo tal como a Síria. Simultaneamente, senti que a minha responsabilidade é contribuir para o seu desenvolvimento e melhoria em todos os aspetos, para ter um serviço de transporte organizado e sustentável, que garanta a mobilidade e o acesso básico para atender às necessidades de desenvolvimento, sem afetar a qualidade de vida das gerações futuras. Para isso tem de ser seguro, saudável, barato e com menor impacte em termos de poluição e no uso de recursos renováveis e não renováveis, atender às necessidades do presente sem afetar ou prejudicar a harmonia ambiental e a necessidade de alcançar uma economia sustentável a longo prazo e conveniência para a sociedade. O objetivo desta pesquisa é identificar algumas especificidades das cidades da região do Mediterrâneo que possam de alguma forma explicar as dificuldades existentes quanto à eficiência dos seus sistemas de transportes, o crescente predomínio do uso de automóveis, o atraso na melhoria dos meios de transporte ativos, como bem como as reformas da política de transportes que estão a tentar implementar. As semelhanças entre Lisboa e Homs neste aspeto, foram utilizadas para melhor compreender os problemas que essas cidades enfrentam e quais as estratégias a explorar para se chegar a um sistema de transportes mais eficiente e sustentável. Na maioria dos países do sul do Mediterrâneo, as reformas dos transportes estão agora em andamento, mas ainda não apresentam uma boa eficiência quando comparadas com os países do Norte. No entanto, considero as políticas de transporte e gestão da mobilidade urbana de Lisboa como um estudo de caso, para identificar as políticas e medidas que podem ser aplicadas em Homs, ajudando esta cidade a planear de forma mais eficiente o seu sistema de transportes. Como resultado, existe uma interação entre o sistema de transportes e o seu utilizador, dado que estes se influenciam mutuamente. Nesta dissertação centro-me na perspetiva do utilizador. Foram utilizados métodos que se focalizam nas pessoas e revelam os seus pensamentos, conhecimentos, experiências e sentimentos e como o mundo progride

Pricing, Investment, and Network Equilibrium

Despite rapidly emerging innovative road pricing and investment principles, the development of a long run network dynamics model for necessary policy evaluation is still lagging. This research endeavors to fill this gap and models the impacts of road financing policies throughout the network equilibration process. The manner in which pricing and investment jointly shape network equilibrium is particularly important and explored in this study. The interactions among travel demand, road supply, revenue mechanisms and investment rules are modeled at the link level in a network growth simulator. After assessing several measures of effectiveness, the proposed network growth model is able to evaluate the short- and long-run impacts of a broad spectrum of road pricing and investment policies on large-scale road networks, which can provide valuable information to decision-makers such as the implications of various policy scenarios on social welfare, financial situation of road authorities and potential implementation problems. Some issues hard to address in theoretical analysis can be examined in the agent-based simulation model. As a demonstration, we apply the network growth model to assess marginal and average pricing scenarios on a sample network. Even this relatively simple application provides new insights into issues around road pricing that have not previously been seriously considered. For instance, the results disclose a potential problem of over-investment when the marginal cost pricing scheme is adopted in conjunction with a myopic profit-neutral investment policy.Transportation network equilibrium; Road growth; Pricing; Congestion toll; Investment; Transport policy analysis.

GLOBE climate legislation study

The Climate Legislation Study covers over 850 national laws and policies directly related to climate change mitigation and adaptation. Launched in 2010 covering only 16 countries, the study currently covers 99 jurisdictions, which, taken together, produce 93 per cent of global emissions and are home to 90 per cent of the world’s forests. The database includes 46 of the world’s top 50 emitters

Global Innovation Policy Index

Ranks fifty-five nations' strategies to boost innovation capacity: policies on trade, scientific research, information and communications technologies, tax, intellectual property, domestic competition, government procurement, and high-skill immigration

The interface of trade, investment, and competition policies : issues and challenges for Latin America

Latin American countries have not had much experience with competition policy. Restricted trade policies, together with no competition policy, have often resulted in domestic monopolies. Trade liberalization in the 1980s and 1990s has strengthened import competition, but trade policies alone cannot create a competitive economic environment. Trade policy as an instrument of competition policy (limited as it has been) has been constrained by a disproportionate amount of nontraded goods, vertical integration, and distribution monopolies -- and sometimes the use of antidumping, countervailing, and safeguard measures. Competition policies -- such as antitrust laws, merger controls, and other regulatory measures -- can prevent exclusionary practices, collusion among competitors, and the abuse of market power. Allowing foreign ownership and liberalized investment regimes will further enhance domestic competition by adding market presence. The authors contend that trade and competition policies must complement each other and that when they do, welfare improves. Tensions between the policy areas arise because of globalization, regional policies, technical barriers, certain kinds of industrial policy, and macroeconomic exigencies. Trade policy itself can be used for protection even without high tariffs or quantitative restrictions. Antidumping, countervailing, and safeguard measures limit rather than promote competition. These measures -- which should be GATT-compatible by law and competition-promoting in spirit -- must be used judiciously. The authors favor the use of safeguards rather than other measures to provide temporary protection for firms facing import surges. Latin American countries have recently made impressive strides in trade reform, but have made limited use of competition policies. The authors argue for more use of competition policies to enhance gains from trade reform. They also argue for harmonization of competition policies as these countries reduce barriers against each other through regional agreements. More efforts should be made to: 1) create favorable competitive environments; 2) harmonize trade, regulatory, and competition policies as well as conflict resolution mechanisms; and 3) strengthen enforcement mechanisms and make them binding.Trade and Regional Integration,ICT Policy and Strategies,Environmental Economics&Policies,Economic Theory&Research,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT

Reducing structural dominance and entry barriers in Russian industry

Many industrial firms in Russia have undergone changes in ownership, but relatively few have been competitively restructured. Using survey and other data, the author suggests that much of Russian industry is immune from robust competition because of heavy vertical integration, geographic segmentation, and the concentration of buyers and sellers, in selected markets. Moreover, regulatory constraints protect incumbent firms from competition with new entrants, both domestic and foreign. The author sketches a reform agenda for Russia's post-privatization program, which emphasizes the restructuring of anti-competitive structures and the reduction of barriers to entry. The author's proposed reform agenda calls broadly for strengthening Russia's nascent rules-based framework for competition policy to reduce discretion, increase transparency, and improve accountability.Markets and Market Access,Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,Small and Medium Size Enterprises,Environmental Economics&Policies,Economic Theory&Research,Private Participation in Infrastructure,Small Scale Enterprise,Microfinance

EC Bananarama 1992 : the sequel - the EC Commission proposal

Some European Community (EC) countries give preferred market access and high prices to bananas from selected developing countries or EC regional suppliers. This preferential status is regarded as a form of aid to these countries, most of which are developing small island economies. EC marketers of bananas from these preferred suppliers also benefit because of the high retail prices. Nonpreferred suppliers - mainly developing countries of Latin America - are hurt by the policies because access is denied or restricted and the lower demand depresses the world price for bananas. The Community's commitment to establish a single unified EC banana market on December 31, 1992 provides a timely opportunity to reform existing distortionary trade policies. The recently announced proposal of the Commission of ECs to regulate banana trade within a unified market relies on quotas to control imports. The proposal is extremely complicated. It is designed to severely restrict competition and to maintain the advantages of selected groups. The authors update their earlier analysis of world banana trade to reflect the market in 1993. They evaluate the implications of the Commission's proposal alongside existing and alternative policies. They find that current policies cost EC consumers about $1.6 billion annually to transfer a net benefit of$0.3 billion a year to preferred suppliers. So, it costs EC consumers about $5.30 to transfer$1.00 of aid toselect developing countries or regions. Additionally, every dollar of aid reaching preferred suppliers costs other developing country suppliers $0.32. EC marketers are the main beneficiaries. Of the$5.30 cost to EC consumers, over $3.00 is collected as excessive marketing margins by protected importers and wholesalers. About$1.00 is lost in outright waste. Several plausible versions of the Commission's proposal are modelled. At best they are found to be slightly less costly than existing policies and at worst, considerably more costly. A 3.5 percent reduction in the quota allocation is estimated to lead to a 30 percent increase in the cost of the proposal. The authors conclude that the Commission's proposal for a unified EC banana policy appears to be little more than a way of replacing existing distortionary national policies with an almost equally distortionary single policy and market. The only difference: the costs would be borne by consumers in all EC countries rather than consumers in only some countries. Worse still, costs could increase. Markets that now gain the benefits of mostly open and competitive marketing such as Germany would face closed and uncompetitive conditions. For developing countries exporting bananas, the proposal offers little. At best conditions may be no worse than they are now. At worst the policy could hurt Latin American suppliers even more than current policies and introduce considerable confusion about the level of support to preferred suppliers. Under the proposed quota system aid will not be well targeted. A more efficient way of achieving the EC's aid commitment is through a small tariff of about 17 percent, used to fund a system of well-targeted deficiency payments or direct aid. The only reason for choosing the Commission's proposal over simpler, tariff-based options seems to be to maintain the vested interests of protected EC markteters. But this is contrary to the objectives of unification, which are to seek gains from increased competition and trade.Environmental Economics&Policies,Access to Markets,Markets and Market Access,Economic Theory&Research,Consumption