The fourth edition of the glossary for transport statistics is the result of continuing and valuable cooperation between the United Nations Economic Commission for Europe (UNECE), the International Transport Forum (ITF) and Eurostat, that has put a sustained effort into meeting the need to harmonise transport statistics at the international level. The glossary now comprises 735 definitions and represents a point of reference for all those involved in transport statistics. By following the guidance contained within these definitions, a considerable contribution will be given to the improvement in both the quality and comparability of the data. In this fourth edition, published in 2009, the rail, road, inland waterway, pipelines and intermodal chapters have been substantially revised. A new air transport chapter has been added. In rail, the revision takes account of the changing environment facing rail operators, especially in Europe. In addition, a completely new rail accidents section has been added. The road and inland waterway chapters have also benefited from a thorough revision to reflect current concerns. For the inland waterway chapter, an accident section has been added. The pipeline chapter has been extended to cover gas as well as oil pipelines, given their growing importance in supplying the energy market. The new air transport chapter follows the guidance given by ICAO but with some extra input from IATA and ACI.