This article was written in collaboration with WSP Engineer Michael Macniven. It was first presented as a part of the 8th edition of the International Symposium on Tunnel Safety and Security (ISTSS) in Borås, Sweden.

Road tunnel fixed fire fighting systems (FFFS) have made substantial progress in their incorporation. Initially utilized primarily in Asia, they have now become common in Europe and North America.

They have been shown to prevent the spread of fire to nonincident vehicles, and to minimize the damage to road tunnels. This has a significant benefit particularly to critical transportation corridors. Water application rate continues to be the most important design parameter and yet no guidance is provided, leaving designers to figure it out each time. The determination of this parameter is very important as water usage must be optimized, particularly for restricted water supplies.

The ability of these systems to mitigate flammable liquid tanker (FLT) fires is not as well understood. The general practice has been to restrict their use or stipulate foam suppression. Both of these practices are influenced due to industry increased demand for usage. While there is evidence that the same system can provide reasonable mitigation, there is hesitation about allowing it. In short, FFFS implementation could be greatly enhanced by two considerations.

• Providing prescriptive water application rates that reduce the uncertainty in their criteria and objectives.
• Implementing a test program for FLT performance that would help reduce the uncertainty of system performance on these types of fires and allow greater confidence that these fires can be successfully mitigated without foam systems.