Portal message signs

Signs located near tunnel portals mostly indicate certain restrictions/mandatory behaviour with regard to the use of the tunnel.

Typically, regulatory signs at portals are used to indicate:

• The speed limit if it is lower than on the access road (this may simply be a reminder if the speed limit was already indicated further upstream), 
• The mandatory distance between vehicles,
• That overtaking is prohibited for certain vehicle categories,  
• That headlights must be switched on,
• That it is prohibited to stop or to park outside designated areas,
• Whether dangerous goods vehicles are authorised.

These regulatory signs can sometimes be grouped onto a single sign as given in Fig. 1.

Certain countries have a specific « tunnel » sign to which some of the above-mentioned information is added.

Information signs are usually also located near the tunnel portal, providing:

• The name of the tunnel,
• The length of the tunnel,
• The broadcasting of certain FM frequencies within the tunnel.

For tunnels with a height limit that is lower than that of the access road, there is also a sign indicating the maximum authorised height. This sign may also be accompanied by a physical obstacle designed to limit the risk of over-height vehicles hitting tunnel equipment.