Road tunnels are used by millions of people without incident every day. But on the rare occasions when something goes wrong, perhaps with a vehicle fire or collision, they can quickly become extremely hazardous and frightening environments, and one where you need to evacuate people as quickly as possible, or guide them to safe areas and keep them calm.
Mostly, tunnels are unmanned and therefore automatic or remote announcements are critical to ensure safety. In the event of a problem, fire or smoke will rapidly fill a tunnel so the evacuation needs to occur very quickly. This differs from rail tunnels, where the train is designed to keep going through an incident, so the sound system is a last resort.
As demonstrated in many other places used by the public, people tend to ignore a simple alarm but respond and react to a clear voice message telling them what to do.
All new and major refurbishment tunnel projects are installing voice alarm systems to address everyone inside, ensuring they remain calm and informed. These environments create unique challenges for system designers from a physical perspective, as well as conforming with all the relevant standards.