英语翻译In this analysis we use average costs largely derivedfro

英语翻译
In this analysis we use average costs largely derivedfrom aggregate data.While our estimates lack the precision of a more specificcase study,these estimates provide an overall sense of the magnitude ofvarious types of external costs generated by freight rail and trucks relativeto average private costs nationally.If public policies were formulated tointernalize these external costs in an aggregate sense,some carriers of eithermode would overpay,while others would underpay.The amount of overpayment orunderpayment would depend on the difference between average costs in theaggregate and the marginal costs in a particular circumstance.
In short,unless one is able to accurately estimate themarginal social costs of each unit of transportation (e.g.,each ton-mile) inwidely varying circumstances,two choices are possible.One is to ignoreexternal costs and estimate user charges and taxes solely on the basis ofpublic facility use or other services provided by the public sector; the otheris to add some uniform charge to reflect external costs and accept a degree ofcross-subsidization within each transportation mode.The analysis in thisarticle tends toward the second option and develops conservative estimates ofaverage costs in rural areas where the variation in such costs is likely to bemuch less than is the case among different metropolitan areas.

在本文的分析中我们使用平均成本在很大程度上是由聚合数据.虽然我们的估计缺乏一个更specificcase研究精度,这些估计提供了一个整体的意义的幅度、各种类型的外部成本的产生和卡车货运铁路与全国平均的私人成本.如果公共政策的制定tointernalize这些外部成本在总的意义上,一些运营商的eithermode会多付,而其他人会付.orunderpayment多付的金额将取决于组合的平均成本和在特定环境下的边际成本之间的差额.总之,除非你能准确地估计每单位运输边际社会成本（例如,每吨英里）inwidely不同的情况下,两种选择都是可能的.一是ignoreexternal成本和估计用户收费和税收仅仅依据公共设施的使用或其他服务由公共部门提供；二是反映外部成本和在每个运输方式的接受程度不同方向的资助加一些均匀电荷.在本文的分析倾向于第二种选择和发展的保守估计的平均成本在农村地区,这种成本的变化可能比小于不同城市之间的情况下.