National Tunnel Inventory (NTI)

The NTI is an aggregation of structure inventory and appraisal data of tunnels located on public roads submitted by States, Federal agencies and Tribal governments in accordance with the National Tunnel Inspection Standards (NTIS) which requires each State prepare and maintain an inventory of all tunnels. The NTI data is used as a data source to assist in the oversight of the National Tunnel Inspection Program and to respond to inquiries from different entities on the Nation’s tunnels.