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. The thesaurus was later improved through NCHRP Project 20-32(2) and ongoing efforts by TRB and CDB Enterprises, Inc to keep the terminology current with the industry.