The Transportation Research Thesaurus (available at https://trt.trb.org/) presents a consistent approach to indexing transportation information. TRB has adopted the thesaurus as the official list from which Transportation Research Information Services (TRIS) indexing terms, or descriptors, are selected.

Tremendous volumes of information are currently being generated for the planning, design, operation, maintenance, and administration of transportation systems in the United States and abroad. This information, which ranges from specific engineering data to research summaries, is regularly used by federal, state, and local agencies; universities; and other organizations. Storage and retrieval systems have been created to manage and provide access to this information. If the vocabularies of people assigning indexing terms and those seeking the information are not consistent, searchers will miss needed items and retrieve unwanted information. Such difficulties are inherent in any language-based system, but the creation of a thesaurus minimizes the problem.

NCHRP Project 20-32 developed a comprehensive transportation research thesaurus and software to access the thesaurus. Under NCHRP Project 20-32(2), CDB Enterprises, Inc., reviewed the index terms currently used in TRIS, updated the terms in the thesaurus by working extensively with TRIS indexers, and facilitated the conversion of all TRIS records to use the new thesaurus terms. CDB Enterprises also improved the access software. TRB and CDB Enterprises, Incs. have updated the thesaurus since the completion of Project 20-32(2) to keep the terminology current with the industry.

This project also produced NCHRP Report 450, Transportation Research Thesaurus and User's Guide, which is now out-of-print. That report describes the thesaurus and how it should be used when developing index terms for a publication. Much of the information in the report is available through the Help and About screens of the thesaurus viewer.