A new publication by the International Energy Agency (IEA) and the International Union of Railways (UIC) highlights the environmental sustainability of rail transport. The report – Railway Handbook 2012: Energy Consumption and CO2 Emissions – includes the latest information from the UIC and IEA databases. The transport sector is responsible for nearly one quarter of all energy-based carbon dioxide (CO2) emissions worldwide, mainly due to road traffic. Total transport CO2 emissions have constantly increased since 1990 and all transport modes – except railways – have increased their greenhouse gas emissions from fuel combustion. Railway companies operating worldwide produce less than 1% of the total CO2 emissions caused by the transport sector. The report notes that railways have improved energy efficiency significantly over the last two decades by, for example, filling trains more effectively and deploying more fuel efficient rolling stocks (vehicles that move on a railway).