Emergencies in Tunnels

Any emergency in a road tunnel, be it an accident or a fire, is subjectively and objectively dangerous. Our project was thus intended to make road tunnels safer and to quickly and safely instruct road users on how to respond appropriately to disruptions.

The starting point was an online survey of 423 persons of all age groups about their knowledge of tunnel facilities and procedures. Results showed that 16% of respondents would stay in their cars if the tunnel were entirely filled with smoke and fire, for example, while 19% would not know what to do. What is more, 42% of respondents overestimated the time they would have to evacuate in case of fire. An analysis of previous tunnel fires showed that people generally underestimate the urgency of the situation and think of their car as a safe space, which leads them to stay put for too long when faced with smoke and fire.

Visual / Haptic Options

In order to determine how people can be evacuated from a smoke-filled environment as quickly as possible, we conducted an experiment in a bunker facility that incorporated theatrical smoke and loud noise ( n=54) to examine various guidance systems such as chase lights, diode laser modules, handrails, and combinations of these. If the tunnel needs to be crossed to get to the emergency exit, a combination of visual and haptic aids is particularly useful.

Acoustic Options

As part of the study, we developed announcements for conventional horn loudspeakers (poor sound quality) and for modern ones (less distortion and thus easier to understand), radio announcements and acoustic signals for extreme disruptions of normal service. The announcements are short and based on psychoacoustic and linguistic findings.

Acoustic signals and certain sounds in addition or instead of these announcements can be helpful in a tunnel fire. Such signals and sounds must be easy to locate and self-explanatory in order to prompt people to quickly exit their vehicles and make emergency exits easier to find.

In one test series, a number of “beckoning” and “urging” sounds were compared. “Beckoning” sounds to guide the test subjects towards the exit included various bird calls, musical instruments, a singing voice (“This way”), a speaking voice (such as “Please exit here”, “Emergency exit this way”) white noise and others.

Aversive signals used to encourage people to leave their vehicles and the tunnel were created with an organ pipe at about 7 Hz and a bass speaker (25-100 Hz range). Other signals, such as a fire alarm siren, were also tested.

In a tunnel emergency, a “sawtooth” bass sound (period 10 at 50 Hz) or a deep sound from an organ pipe (7 Hz) are best suited to getting people to leave their vehicles and escape. Such low frequencies can be felt in the abdomen and are perceived as highly unpleasant. These sounds are the most likely to be interpreted correctly and the emotions they elicit are suitable to get people to leave the tunnel. The fire alarm siren, however, does not work to get people to leave their vehicles and find the emergency exit as it is associated with the impression that help is on the way. 

Contrary to previous suggestions in the literature, white noise (without additional sounds) does not work to draw people to the emergency exit in the noisy environment of a tunnel.

Much better suited is a female alto voice singing “This way” in a drawn-out sing-song (descending minor third), alternating with European Robin song played over white noise. Alternating “Emergency exit this way” with European Robin song played over white noise and “Please exit here” also works.

These combinations of signals are easy to locate, are likely to be interpreted correctly and are rated positively.

The different systems must be hierarchically coordinated based on the different service disruptions and emergency scenarios. The results of this study can be implemented with relatively little effort and would improve safety in tunnels in any kind of such incident.




Färber, Brigitte; Färber, Berthold: Verhaltensanweisungen bei Notsituationen in Straßentunneln, Bremerhaven, Wirtschaftsverlag NW 2010