Forecasting and Evaluating Network Growth

This research assesses the implications of existing trends on future network investment, comparing alternative scenarios concerning budgets and investment rules across a variety of performance measures. The main scenarios compare 'stated decision rules';, processes encoded in flowcharts and weights developed from official documents or by discussion with agency staff, with 'revealed decision rules', weights estimated statistically based on observed historical behavior. This research specifies the processes necessary to run the network forecasting models with various decision rules. Results for different scenarios are presented including adding additional constraints for the transportation network expansion and calibration process details. We find that alternative decision rules make only small differences in overall system performance, though they direct investments to very different locations. However, changes in total budget can make a significant difference to system-wide performance.

A Decision Model for E-commerce-enabled Partial Market Exit

Struggling retail chains often try to recover profitability by closing some of their stores. The challenge in this strategy lies in determining how many stores to close, as store exit has implications for both the customers and the supply chain. After a store closes, its customers are lost forever to the competition, unless there is a surviving open store nearby or an electronic alternative such as an e-store. From the supply chain perspective, after a store closes, its supporting regional distribution center is left with less business, and thus reduced viability. This paper develops a decision support model to study the profitability of alternative retail network structures by varying the proportion of stores that are closed, the average price sensitivity of demand, the price difference between the online store and the traditional retailers, and customer retention rates

The reform of fiscal systems in developing and emerging market economies : a federalism perspective

The authors review experiences with fiscal federalism in industrial countries and present a framework for a reform of fiscal systems in developing and transition economies. They indicate how the benefits of decentralized decisionmaking in a federal system can be achieved in a manner consistent with the objectives of national efficiency and equity. The following are their suggestions. Decentralization can be made compatible with national objectives through conditional grants, regulation, or coordinated decisionmaking. The federal government should assume primary responsibility for providing national public goods and services, for efficiency of the internal common market, for redistributive equity, for external relations, and for macroeconomic policy. State governments should be responsible for subnational public goods and services, for the delivery of quasi-private goods and services, (such as education, health, and social insurance), for fiscal equity among municipalities, and for overseeing local government decisionmaking. Local governments should be responsible for purely local services. Where jurisdiction for a public service is shared, the roles of the various levels of government should be clarified. Accountability should be hierarchical, with the federal government responsible for overall policy and standards, and lower levels of government with the actual delivery of services and infrastructure. In some cases, asymmetric decentralization may be the preferred option, especially where jurisdictions differ greatly in size and population. Efficiency and equity must be considered in assigning taxes. Efficiency considerations suggest centralizing taxes applied on more mobile bases (such as taxes on capital income and on trade). Equity considerations suggest centralizing progressive income taxes and transfers to persons as well as taxes on wealth and wealth transfer and on resource rents. States could use excise taxes or general sales taxes if levied on a single-stage basis; if a multistage sales tax is used, it is best administered centrally. States could also obtain revenues from piggy-backing on the federal income tax provided a harmonized system is maintained. Municipalities should use property taxes, user fees, and licenses. Tax and expenditures assignment must be supplemented by a system of fiscal transfers, both because the desirability of greater decentralization of expenditures than of taxes will give rise to fiscal imbalances and because transfers are a necessary instrument for achieving efficiency and equity in a decentralized federation. In a decentralized federation, fiscal inefficiencies and fiscal inequities will occur because states will not deliver comparable sets of services at comparable tax rates. Eliminating these differential net fiscal benefits requires a set of equalizing unconditional transfers, possibly combined with a more general revenue-sharing scheme. Matching conditional grants are useful for internalizing the spillover of benefits from state public spending to residents of neighboring states. More important is the use of federal-state conditional grants as a means for the federal government to achieve national efficiency and equity objectives while allowing public service delivery to be decentralized. In transition economies, framework laws on property rights, corporate legal ownership and control bankruptcy, and financial accounting and control are not fully developed. This should be a high priority. The lack of local administrative experience, institutions, and competence should not be used as an excuse for not decentralizing responsibilities. If necessary, transitional funding and training should be provided.National Governance,Environmental Economics&Policies,Economic Theory&Research,Public Sector Economics&Finance,Banks&Banking Reform

Optimized shunting with mixed-usage tracks

We consider the planning of railway freight classification at hump yards, where the problem involves the formation of departing freight train blocks from arriving trains subject to scheduling and capacity constraints. The hump yard layout considered consists of arrival tracks of sufficient length at an arrival yard, a hump, classification tracks of non-uniform and possibly non-sufficient length at a classification yard, and departure tracks of sufficient length. To increase yard capacity, freight cars arriving early can be stored temporarily on specific mixed-usage tracks. The entire hump yard planning process is covered in this paper, and heuristics for arrival and departure track assignment, as well as hump scheduling, have been included to provide the neccessary input data. However, the central problem considered is the classification track allocation problem. This problem has previously been modeled using direct mixed integer programming models, but this approach did not yield lower bounds of sufficient quality to prove optimality. Later attempts focused on a column generation approach based on branch-and-price that could solve problem instances of industrial size. Building upon the column generation approach we introduce a direct arc-based integer programming model, where the arcs are precedence relations between blocks on the same classification track. Further, the most promising models are adapted for rolling-horizon planning. We evaluate the methods on historical data from the Hallsberg shunting yard in Sweden. The results show that the new arc-based model performs as well as the column generation approach. It returns an optimal schedule within the execution time limit for all instances but from one, and executes as fast as the column generation approach. Further, the short execution times of the column generation approach and the arc-indexed model make them suitable for rolling-horizon planning, while the direct mixed integer program proved to be too slow for this. Extended analysis of the results shows that mixing was only required if the maximum number of concurrent trains on the classification yard exceeds 29 (there are 32 available tracks), and that after this point the number of extra car roll-ins increases heavily

An Incentive Compatible, Efficient Market for Air Traffic Flow Management

We present a market-based approach to the Air Traffic Flow Management (ATFM) problem. The goods in our market are delays and buyers are airline companies; the latter pay money to the FAA to buy away the desired amount of delay on a per flight basis. We give a notion of equilibrium for this market and an LP whose solution gives an equilibrium allocation of flights to landing slots as well as equilibrium prices for the landing slots. Via a reduction to matching, we show that this equilibrium can be computed combinatorially in strongly polynomial time. Moreover, there is a special set of equilibrium prices, which can be computed easily, that is identical to the VCG solution, and therefore the market is incentive compatible in dominant strategy.Comment: arXiv admin note: substantial text overlap with arXiv:1109.521

Microsimulation models incorporating both demand and supply dynamics

There has been rapid growth in interest in real-time transport strategies over the last decade, ranging from automated highway systems and responsive traffic signal control to incident management and driver information systems. The complexity of these strategies, in terms of the spatial and temporal interactions within the transport system, has led to a parallel growth in the application of traffic microsimulation models for the evaluation and design of such measures, as a remedy to the limitations faced by conventional static, macroscopic approaches. However, while this naturally addresses the immediate impacts of the measure, a difficulty that remains is the question of how the secondary impacts, specifically the effect on route and departure time choice of subsequent trips, may be handled in a consistent manner within a microsimulation framework. The paper describes a modelling approach to road network traffic, in which the emphasis is on the integrated microsimulation of individual trip-makers’ decisions and individual vehicle movements across the network. To achieve this it represents directly individual drivers’ choices and experiences as they evolve from day-to-day, combined with a detailed within-day traffic simulation model of the space–time trajectories of individual vehicles according to car-following and lane-changing rules and intersection regulations. It therefore models both day-to-day and within-day variability in both demand and supply conditions, and so, we believe, is particularly suited for the realistic modelling of real-time strategies such as those listed above. The full model specification is given, along with details of its algorithmic implementation. A number of representative numerical applications are presented, including: sensitivity studies of the impact of day-to-day variability; an application to the evaluation of alternative signal control policies; and the evaluation of the introduction of bus-only lanes in a sub-network of Leeds. Our experience demonstrates that this modelling framework is computationally feasible as a method for providing a fully internally consistent, microscopic, dynamic assignment, incorporating both within- and between-day demand and supply dynamic