Práctica de tankering en las líneas aéreas españolas.

La diferencia en los precios del queroseno de aviación vigentes en diferentes aeropuertos puede hacer ventajoso, desde un punto de vista económico, cargar combustible en exceso en los lugares de menor precio, aún a costa de incrementar el peso operativo del avión y, por tanto, el consumo total. Esta práctica, conocida en la industria con el nombre anglosajón de tankering, se ha visto incentivada por la liberalización de los precios energéticos en la UE, que permite variar tarifas, según los distintos costes de refino, transporte y almacenamiento. En esta ponencia se desarrolla un planteamiento analítico para determinar las cantidades óptimas de carga de combustible en función de sus precios relativos, las distancias de los vuelos individuales y los tipos de avión empleados, tanto en los casos de vuelos de ida y vuelta, como en la realización de una cadena de vuelos por distintos aeropuertos. Posteriormente se exponen los resultados de una encuesta efectuada en el año 2008 entre los mayores operadores de aviación comercial en España, de la que se obtiene una estimación del exceso de consumo por la práctica de tankering, sus repercusiones ambientales por aumento de emisiones contaminantes y los beneficios económicos obtenidos por las compañías aéreas. Finalmente, se proponen algunas opciones para reducir o eliminar la práctica de tankering, con las mínimas consecuencias económicas para las líneas aéreas y compañías suministradoras de queroseno, teniendo en cuenta las mejores prácticas de los operadores aéreos y los mecanismos de formación de precio de los suministradores de combustibl

Optimizing Fueling Decisions for Locomotives in Railroad Networks

Even though rail transportation is one of the most fuel efficient forms of surface transportation, fueling costs are one of the highest operating cost head for railroad companies. In US, unlike Europe, fueling costs are indeed, by far, the single highest operating cost. For larger companies with several thousands of miles of rail network, the fuel bills often run into several billions of dollars annually. The railroad fueling problem considered in this paper has three distinct cost components. Fueling stations charge a location dependent price for the fuel in addition to a fixed contracting fee over the entire planning horizon. In addition, the railroad company must also bear incidental and notional costs for each fuelling stop. It is imperative that the number of fueling stops between an origin and destination should be restricted to avoid unnecessary delays. This paper proposes a mixed integer linear program model that determines the optimal strategy for contracting and fuel purchase schedule decisions that minimizes overall costs under certain reasonable assumptions. This model is tested on a large, real-life problem instances. This mathematical model is further enhanced by introducing several feasible MIP cuts. This paper compares the efficiency of different MIP cuts in order to reduce the run-time. Lastly, the paper concludes with an observation that even though the problem scale was expected to diminish the model performance, it was indeed noted that run-time and memory requirements are fairly reasonable. It thus establishes that this problem must be looked beyond the prism of heuristics and other approximate algorithms for actual implementation at railroad companies

Going Bunkers: The Joint Route Selection and Refueling Problem

Managing shipping vessel profitability is a central problem in marine transportation. We consider two commonly used types of vessels—“liners” (ships whose routes are fixed in advance) and “trampers” (ships for which future route components are selected based on available shipping jobs)—and formulate a vessel profit maximization problem as a stochastic dynamic program. For liner vessels, the profit maximization reduces to the problem of minimizing refueling costs over a given route subject to random fuel prices and limited vessel fuel capacity. Under mild assumptions about the stochastic dynamics of fuel prices at different ports, we provide a characterization of the structural properties of the optimal liner refueling policies. For trampers, the vessel profit maximization combines refueling decisions and route selection, which adds a combinatorial aspect to the problem. We characterize the optimal policy in special cases where prices are constant through time and do not differ across ports and prices are constant through time and differ across ports. The structure of the optimal policy in such special cases yields insights on the complexity of the problem and also guides the construction of heuristics for the general problem setting

Indicadores de desempenho de companhias aéreas e seus impactos na eficiência operacional

Airlines must constantly evaluate the costs and efficiency of their operational performance indicators to establish a competitive business market strategy. This study aims to investigate the relevance of some performance indicators of airline´s management and operational efficiency. With the use of a panel data regression for the four largest private Brazilian airlines – Avianca, Azul, Gol, and Latam, from 2009 to 2017, the results show that operational efficiency is achieved when there is a greater offer of routes and flight frequency to meet passenger demand, generating higher revenue passenger kilometer (RPK). On the other hand, shorter stage length and reduced takeoff numbers affect inversely proportional the operating efficiency as a function of fuel consumption and energy capacity. Through the analysis of these performance indicators, it is possible to determine strategies that support decision making to increase the operational efficiency of airlines.As companhias aéreas devem avaliar constantemente os custos e a eficiência dos indicadores de desempenho de suas operações para estabelecer uma estratégia de negócio competitiva. Este estudo tem como objetivo investigar a relevância de alguns indicadores de desempenho na gestão e eficiência operacional de companhias aéreas. Com o uso de uma regressão de dados em painel referente às quatro maiores companhias aéreas brasileiras até o momento dos dados considerados no estudo (2009 a 2017) - Avianca, Azul, Gol e Latam, os resultados demonstram que a eficiência operacional é alcançada quando há uma maior oferta de rotas e frequência de voos para atender à demanda de passageiros, gerando maior receita por passageiro-quilômetro (RPK). Por outro lado, a etapa de voo mais curta e o número reduzido de decolagens afetam de forma inversamente proporcional a eficiência operacional em função do consumo de combustível e eficiência energética das aeronaves. Por meio da análise desses indicadores de desempenho, é possível definir estratégias que subsidiam a tomada de decisão para aumentar a eficiência operacional das companhias aéreas