Road Tunnels Manual

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Portal message signs

Signs located near tunnel portals mostly indicate certain restrictions/mandatory behaviour with regard to the use of the tunnel.Fig.1: Regulatory signs grouped together onto a single sign at the Mont Blanc tunnel portal

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:

Figure 2: Signs at a portal showing the length of the tunnel and the distance to be kept between vehicles

  • 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.

Reference sources

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