There is considerable variation in the average cost of operations across urban rail transport (or metro) systems. Since metros are typically owned and operated by public authorities, there is a public interest case in understanding the key drivers of their operational costs. This paper estimates short-run cost functions for metro operations using a unique panel dataset from twenty-four metro systems around the world. We use a flexible translog specification and apply dynamic panel generalised method of moments (DPGMM) estimation to control for confounding from observed and unobserved characteristics of metro operations. Our empirical results show that metro systems with a high density of usage are the most cost-efficient. We also find that operational costs fall as metro size increases. These results have important implications for the economic appraisal of metro systems.

整个城市轨道交通（或地铁）系统的平均运营成本差异很大。由于地铁通常由公共机构拥有和运营，因此在了解运营成本的主要驱动因素方面存在公众利益。本文使用来自全球二十四个地铁系统的唯一面板数据集，估算了地铁运营的短期成本函数。我们使用灵活的对数规范，并应用动态面板广义矩量法（DPGMM）估计，以控制地铁运营中观察到和未观察到的特征造成的混淆。我们的经验结果表明，具有高使用密度的地铁系统是最具成本效益的。我们还发现，运营成本随着地铁规模的增加而下降。