The Transportation Research Thesaurus (TRT) is an important tool for vocabulary control. The National Transportation Library provides it here both as a tool for searching TRIS Online, the NTL Catalogs and other developing resources, and as a tool for indexers, catalogers and researchers in developing their own resources. TRT is maintained by the TRANSPORTATION RESEARCH BOARD. The NTL keeps this copy up to date using information from the TRB. The date of the latest update is 10/01/2008.