It takes time from the emergency services are notified until they arrive at the tunnel. This must also road users know and the road authority have the responsibility that this assumption is known.

Safety equipment are quite important when it comes to tunnels without any possibilities to escape from one tube to another. Maybe in some cases there are 5 to 10 kilometre to the nearest portal. Early notification to the motorists can be crucial for the outcome of a critical incident or fire.

When it comes to understanding the critical situation, there may be a delay before the individual road user understand and can decide what to do to rescue themselves. Road users need information and decision support to ensure that this phase is as short as possible. This can be provided through notification via radio broadcast, public address system and eventually other measures as a result of technological developments.

Public address systems has been used for tunnels in Europe for several years. The systems has mainly been installed in 2 tube tunnels with unidirectional traffic an the messages is easy to perceive. To install these systems in bidirectional tunnels and make sure that the road user can perceive the message is an other challenge. To handle the delay in both directions has been difficult to configure.

The Norwegian Public Roads Administration has decided that long bidirectional tunnels shall be equipped with public address systems, and is now specifying these systems for these tunnels. 

Video: Test of PA system in Vagsbygdporten tunnel in Norway (norwegian annoncement).