As cities work to reduce their total greenhouse gas (GHG) emissions, the transportation sector is lagging, accounting for a growing percentage of total emissions in many cities. The provision of public transit, and specifically urban rail transit, is widely seen as a useful tool for reducing urban transportation GHG emissions. More research, however, is needed to understand the net impact of new metro rail infrastructure on urban emissions and guide efforts to maximise the GHG savings through rail investments. This paper examines the net GHG emissions of the Jubilee line extension (JLE) in London, UK. The GHG emissions associated with construction, operation, ridership and changes in urban density associated with the provision of the new metro rail infrastructure are assessed. These components are then combined and compared to calculate the net GHG impact across the study period, which extends from opening in 1999 through 2011. The capital GHG emissions from construction of the JLE are calculated as 530 kilotonnes carbon dioxide equivalent (CO₂e). The initial mode shift from other rail lines and long-term mode change from automobiles result in yearly GHG savings from riders on the JLE. A quasi-experimental analysis of land-use change near the JLE finds no calculable GHG saving from increased residential density. The GHG payback period is calculated between 13 and 19 years.

中文翻译：

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英国伦敦银禧线扩建对温室气体的净影响

随着城市努力减少其温室气体总排放量，交通运输部门正在落后，在许多城市中占总排放量的比例越来越高。公共交通，特别是城市轨道交通的提供，被广泛认为是减少城市交通温室气体排放的有用工具。然而，需要更多的研究来了解新的地铁轨道基础设施对城市排放的净影响，并指导通过铁路投资最大程度地节省温室气体的努力。本文研究了英国伦敦银禧延长线（JLE）的净温室气体排放量。评估与新地铁基础设施建设相关的建筑，运营，乘客量和城市密度变化相关的温室气体排放。₂ e）。其他铁路线的初始模式转换和汽车的长期模式转换可导致JLE车手每年节省温室气体。JLE附近土地利用变化的准实验分析发现，随着居民密度的增加，无法节省可计算的温室气体。温室气体回收期在13至19年之间。