Provides definitions for six environmental key performance indicators - or "KPIs" - for railway companies (operators, infrastructure managers or integrated companies) as well as explanations on how to produce them. The six indicators are: a) Energy consumption (traction only), b) Share of renewable energy (energy mix and bio-diesel), c) Greenhouse gas emissions (CO[2]), d) Local air pollution (PM and NO[x]), e) Noise emissions, f) Land take (area).