This paper examines the impact of urban light rail systems on congestion, travel time and pollution. Drawing on data from mid-size European cities, I estimate the impact of supply changes for the entire sample and applied a differences-in-differences analysis to a sample of cities that did not have rail systems in the initial year of the considered period. I find evidence that an increase in the supply of rail transport leads to less congestion, less travel time and less pollution. Furthermore, cities with a new rail system have on average 7% less congestion, 1% less travel time and 3% less pollution than cities with no rail systems. The results suggest that light rail systems have been successful in containing the negative externalities associated with car traffic in mid-size European cities.

本文研究了城市轻轨系统对交通拥堵，出行时间和污染的影响。利用来自欧洲中型城市的数据，我估计了整个样本的供应变化的影响，并在考虑期间的第一年对没有铁路系统的城市样本进行了差异差异分析。我发现有证据表明，铁路运输供应的增加可减少交通拥堵，减少旅行时间并减少污染。此外，与没有铁路系统的城市相比，拥有新铁路系统的城市平均拥堵减少了7％，出行时间减少了1％，污染减少了3％。结果表明，轻轨系统已经成功地遏制了欧洲中型城市与汽车交通相关的负面外部影响。