Tunnel functional systems refer to a variety of equipment critical to the operation of road tunnels, such as lighting, ventilation, power supply, and fire-fighting systems. These systems are inspected, at a minimum, every 2 years. Tunnel owners are required to notify the Federal Highway Administration within 24 hours of a critical finding for a tunnel functional system in a tunnel and actions to address the finding in a timely manner.

The objective of this synthesis is to document methods and practices employed by departments of transportation (DOTs) to identify critical findings for tunnel functional systems. The synthesis looked at how DOTs define critical findings, the specific criteria they employ in identifying critical findings, and the processes they follow to address these systems-related issues.

Information for this study was gathered through a literature review, a survey of state DOTs, and follow-up interviews with selected DOTs. Case examples of five DOTs provide additional information on critical findings for tunnel functional systems.

Martha Averso, Ben Margerum, and Brian Seip, Gannett Fleming, Inc., collected and synthesized the information and wrote the report, along with Gary English, Underground Command and Safety, LLC. The members of the topic panel are acknowledged on page iv. This synthesis is an immediately useful document that records practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As progress in research and practice continues, new knowledge will be added to that now at hand.

Completed report can be found at NCHRP Synthesis Report 607.