Tunnels are either open to all vehicles or restricted to certain vehicles.
If they are restricted to certain categories of vehicles (over-sized vehicles, dangerous goods vehicles), alternative routes must be available and clearly indicated as shown in the example below.
If a tunnel is completely closed, due to an accident, road works etc, all users must be informed of the various alternative routes. It is necessary to provide information to users as far upstream as possible, before the relative points of choice, which are sometimes located at a considerable distance from the tunnel. If the tunnel is part of an urban network, other signage means can be used to facilitate the management of diverted traffic (e.g. variable message signs).
For users who are relatively close to the tunnel, they must be informed of the closure and the alternative route before the last point of choice.