Figure 1: Maintenance tasks carried out on tunnel lighting
Chapter 2 of technical report 2008R15 "Operation of existing urban road tunnels" defines the conditions for carrying out maintenance when the tunnel is in operation.
The same difficulties as those mentioned above are likely to be encountered during a refurbishment of equipment in a tunnel that cannot be closed down easily. With regard to maintenance interventions, this type of works may require several weeks, or even several months to be completed. Consequently, more elaborate (and often costlier) measures have to be planned.
Chapter 6 of technical report 05.13.B "Renovation of tunnels" discusses aspects relating to refurbishment.