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Equipment maintenance

Road tunnel security requirements have gradually lead to the installation of a large number of management infrastructures in tunnels.

These installations in tunnels are intended to:

  • reduce the risk of an incident,
  • detect incidents more quickly,
  • take the necessary measures to reduce their impact.

This equipment is controlled by dedicated surveillance teams 24/7.

It requires maintenance in order to function correctly.


The installations in the tunnels require an electricity supply.

Electrical installations and supply

In additional to a conventional electricity supply, the tunnel’s vital emergency installations are equipped with an uninterruptible power supply (power inverter and batteries).

This mainly concerns the emergency lighting, emergency inset lighting, video surveillance, radio communications and dynamic signalling.


Signalling and closure systems

Tunnels may be equipped with Variable Message Signs (VMS), Lane Allocation Signs (LAS), traffic signals and barriers.

These are operated using pre-established scenarios (tunnel closure, lane closure, deviation etc.). They can also be controlled independently of each other.

[Experimentation of remote controlled barriers on tunnels in the Ile-de-France region >]



Tunnels are lit to ensure that any obstacles are fully visible and to guide users.


Lighting installations in tunnels come under two distinct categories:

-   Standard lighting along the full length of the structure which is permanently illuminated according to operating modes which adapt to the time of day and outside light levels,

- Additional lighting which allows the driver’s eyes to adapt progressively from the high outside luminance to the ambient luminance  inside the tunnel.



Almost all tunnels more than 300 metres long are equipped with a mechanical ventilation system to preserve the quality of air inside the tunnel and to remove smoke in the event of a fire.


The ventilation of road tunnels has two main purposes:

- to maintain good air quality inside the structure by diluting polluting vehicle emissions ,

- to contain and/or remove smoke in the event of a fire, as this is the main danger for users.

There are two types of ventilation:

- longitudinal: Using ceiling-mounted jet fans,

- transverse: Using ventilation ducts with external outlets


Video surveillance and Automatic Incident Detection (AID)

Video surveillance is used for the permanent visual monitoring of traffic in the tunnel.

However, the operator cannot simultaneously follow events on several  different monitors. In the 1990s, advances in digital imaging have made it possible to develop Automatic Incident Detection (AID) systems. Implementing these systems in tunnel control centres helps the operator to monitor structures by providing information on incidents which may put users in danger. In these conditions, the operator can trigger the best-adapted intervention scenario as rapidly as possible.



Radiocommunications are used to protect users.


Emergency and information messages can be disseminated to users via their car radios, providing information on how they should react to a given incident. For example, in the event of  a fire these emergency messages facilitate the evacuation of users, thereby limiting personal harm to users.

They are also of vital importance for the emergency services. The emergency services involved must have continuous radio coverage in the tunnel and associated structures (service tunnel, ventilation shafts etc.) in order to coordinate their interventions and improve effectiveness.


Telecommunications and information technology networks

A tunnel installation requires constant information exchange between the equipment and centralised technical management, using new information and communication technologies.

Fibre optics, copper cables and radio waves are the media used for these vocal, data and image exchanges.


Control systems and centralised technical management

The objective of centralised technical management is to provide the operator with the means for managing the operation of the structure.

In Traffic Engineering Management Centres (TEMC), centralised technical management takes the form of Human-Machine Interfaces (HMI).

At the TEMC, the traffic status is displayed for the operator who can control the systems in the tunnel such as ventilation, lighting, dynamic signalling, power supply, and the fire-fighting water network etc.