Tunnels represent a significant financial investment with challenging design, construction, and operational issues. Tunnels that are not adequately maintained usually require more costly and extensive repairs. To help safeguard tunnel users and to ensure reliable levels of service, the FHWA developed the National Tunnel Inspection Standards (NTIS), the Tunnel Operations Maintenance Inspection and Evaluation (TOMIE) Manual, and the Specifications for National Tunnel Inventory (SNTI). In accordance with the NTIS, this Manual describes methods for improving the safety and performance of roadway tunnel operation, maintenance, inspection, and evaluation programs.