Strategic sampling for large choice sets in estimation and application

Many discrete choice contexts in transportation deal with large choice sets, including destination, route, and vehicle choices. Model estimation with large numbers of alternatives remains computationally expensive. In the context of the multinomial logit (MNL) model, limiting the number of alternatives in estimation by simple random sampling (SRS) yields consistent parameter estimates, but estimator efficiency suffers. In the context of more general models, such as the mixed MNL, limiting the number of alternatives via SRS yields biased parameter estimates. In this paper, a new, strategic sampling scheme is introduced, which draws alternatives in proportion to updated choice-probability estimates. Since such probabilities are not known a priori, the first iteration uses SRS among all available alternatives. The sampling scheme is implemented here for a variety of simulated MNL and mixed-MNL data sets, with results suggesting that the new sampling scheme provides substantial efficiency benefits. Thanks to reductions in estimation error, parameter estimates are more accurate, on average. Moreover, in the mixed MNL case, where SRS produces biased estimates (due to violation of the independence of irrelevant alternatives property), the new sampling scheme appears to effectively eliminate such biases. Finally, it appears that only a single iteration of the new strategy (following the initialization step using SRS) is needed to deliver the strategy’s maximum efficiency gains.     

广西道路客运企业战略转型对策研究

文章阐述了广西道路客运企业转型的必要性和紧迫性,分析了道路客运的优势,提出了道路客运企业转型的基本思路,并深入探讨了道路客运企业转型的对策。     

浅谈公路养护建设行业的安全文化建设

文章结合公路养护建设行业安全生产的特点,分析了公路养护建设行业安全文化建设的途径和方法,指出加强安全文化建设,提高员工整体素质,是消除安全隐患,减少事故发生机率的重要手段.     

Strategic considerations behind the network–regional airline tie ups – A theoretical and empirical study

The paper examines the strategic vertical relationship between network and regional airlines. We develop a model to illustrate how network airlines can use the contractual relationship with regional airlines as an efficient tool to simultaneously drive out inefficient network airlines and also accommodate other cost efficient network airlines in any specific market. The model is tested on U.S. data using simultaneous and sequential choice models. We find that market size, cost differences between network airlines, as well as cost differences between network and regional airlines, are the chief determinants of the network airlines’ decisions on whether or not to serve a market with their own fleet, as well as how many regional airlines to contract with.     

Airport management: a strategic approach

In this paper a Dynamic Balanced Scorecard (DBSC) is used for the main purpose of indicating strategy implementation avenues to managers so as to equip them with more efficient decision-making tools. To that end, Fuzzy Multicriteria Decision-Making methodology is used as a source of technical support in formulating a cause and effect system and fuzzy strategic indicators. This methodological instrument brings a strategic vision to performance analysis and is designed to furnish a tool for evaluating the impacts of management action on the BSC fuzzy indicators. The proposed analytical methodology is applied to Brazil’s seven main international airports.     

道路运输企业物流化的阶段划分与策略选择

"物流化"是当今道路运输企业发展的必然趋势。文章在对道路运输企业物流化进行阶段划分的基础上,通过研究道路运输企业物流化的战略目标定位问题,提出了加快道路运输企业物流化步伐的策略。     

The impact of strategic management and fleet planning on airline efficiency - A random effects Tobit model based on DEA efficiency scores

As a result of the liberalisation of airline markets; the strong growth of low cost carriers; the high volatility in fuel prices; and the recent global financial crisis, the cost pressure that airlines face is very substantial. In order to survive in these very competitive environments, information on what factors impact on costs and efficiency of airlines is crucial in guiding strategic change. To evaluate key determinants of 58 passenger airlines’ efficiency, this paper applies a two-stage Data Envelopment Analysis (DEA) approach, with partially bootstrapped random effects Tobit regressions in the second stage. Our results suggest that the effects of route optimisation, in the sense of average stage length of the fleet, are limited to airline technical efficiency. We show that airline size and key fleet mix characteristics, such as aircraft size and number of different aircraft families in the fleet, are more relevant to successful cost management of airlines since they have significant impacts on all three types of airline efficiency: technical, allocative and, ultimately, cost efficiency. Our results also show that despite the fuel saving benefits of younger aircraft, the age of an airline’s fleet has no significant impact on its technical efficiency, but does have a positive impact on its allocative and cost efficiency.