When the tunnel equipment no longer fulfils the needs of the operator or the tunnel users or when the requirements of legislation or the characteristic of the traffic has changed, it may be necessary to upgrade the tunnel.
The need for pre-planned work can be the consequence of, for instance, new regulations or opportunities to improve equipment, its functionality, safety or energy-efficiency, or to reduce preventive maintenance requirements. There may be a further occasional need to replace equipment due to age deterioration. Major work will usually be treated as special projects.
Activities may include:
This chapter of the Manual is broken down into six pages:
Due to the amount of technical equipment in an urban road tunnel it is of utmost importance to keep all documentation about the equipment up to date, not only after major refurbishments, but whenever a change is made.
A refurbishment usually requires updating documentation of:
When planning a major refurbishment it is recommended to use the same approach as for a new design.
General recommendations on refurbishment can be found in the PIARC Report 2008R15EN "Urban road tunnels : recommendations to managers and operating bodies for design, management,operation and maintenance".
If the tunnel design and equipment no longer fulfil the requirements of the operator, the tunnel users or legislation, it may be necessary to refurbish and/or upgrade the tunnel.
During refurbishment or upgrading, it is important to:
Safety of both workers and tunnel users can be influenced by completing refurbishment/upgrading activities in the shortest period possible and every effort should be made to avoid delays in the progress of work. Well planned and efficiently implemented works can effectively reduce the length of these periods.
For both tunnel users and workers, total closure of all tunnel tubes during refurbishment/upgrading obviously provides a much higher level of safety. Workers are protected from traffic and teams can work on all facilities throughout the full length of the tunnel. For traffic, accident risks linked to the implementation of temporary traffic control measures within the tunnel are avoided.
In certain cases it is impossible to close the tunnel entirely. For instance, if the tunnel is the only reasonable means of crossing a strait or a mountain ridge, where alternative routes are not possible, not practicable or very expensive. In these cases refurbishment/upgrading of structures and installations have to be performed while the tunnel remains in service.
Partial closure of one or more lanes is possible during refurbishment/upgrading activities, but working in a tunnel while traffic is present is dangerous for the personnel and requires specific measures to protect them (e.g. the construction of temporary barriers to separate workers from the traffic).
In twin-tube tunnels, one tube can be closed for refurbishment while bi-directional traffic flow is allowed in the other tube. However, this solution is far from ideal and should only be adopted if it is not possible to divert traffic onto an alternative route. Whilst it obviously protects the safety of workers, this situation leads to the users driving in opposing directions within a tube where they are accustomed to traffic moving in only one direction. This can induce a potential increase in accident rates and should be avoided in heavily trafficked tunnels. In tunnels with low to moderate traffic, the risk of accidents can be reduced by the use of VMS and overhead lane control signs. In the case of three-lane tubes, the centre lane should, if possible, be kept free of traffic and act as a buffer safety zone.
In all cases where there are plans to alter the usual traffic configuration in a tunnel, additional safety measures should be implemented: reduced speed limit, closure of slip roads in the vicinity of the tunnel and the implementation of safety exercises in collaboration with emergency services under similar “works” conditions.
Finally, each time the lane/tube/tunnel is reopened to traffic following a closure, great attention must to be given to clearing and cleaning the road to prevent accidents caused by tools and materials in the tunnel or on the road. Similarly, any temporary or uncompleted works must be satisfactorily secured and made safe for the following operating period.
Additional information on refurbishment/upgrading can be found in chapter 6 "Renovation of tunnels" of technical report 05.13.B.
Tunnel refurbishment/upgrading should be conducted in such a way that the negative impact on the environment is as low as reasonably practicable. This can be obtained by:
Tunnel refurbishment/upgrading can in many cases provide an opportunity to improve the environmental impact of the infrastructure as a whole, either through changes to the tunnel’s design or to its equipment.
In terms of design, an example of a major refurbishment project conducted with environmental issues in mind is the Croix Rouse tunnel in Lyon (France). In order to upgrade the tunnel’s safety standards, the initial tube has been linked to a new parallel escape gallery via cross-passages every 150 metres, thereby enabling the evacuation of users. The tunnel owner wished to give additional functions to this escape gallery by allowing its use by public transport (buses) and environmentally-friendly modes such as pedestrians and cyclists. This is an interesting example of the sustainable use of infrastructure for purposes other than those for which it was initially intended.
In terms of tunnel equipment, refurbishment/upgrading can provide an opportunity to reduce energy consumption. The main energy-consuming families of equipment in a tunnel during normal operation are lighting, ventilation, safety devices (signalling, closed circuit television CCTV, etc.) and pumping facilities (in subsea tunnels or when there is water seepage). The respective share of each of these energy-consuming systems varies greatly, depending on the specific characteristics of the tunnel: length, gradient, water ingress, etc. In terms of optimization during refurbishment/upgrading, lighting and ventilation systems are those which provide the highest potential energy savings.
Actions taken on lighting during refurbishment/upgrading are primarily designed to better define the lighting requirements in the entrance zone, which is the most heavily lit. Solutions implemented may:
Other actions may concern the optimization of interior zone lighting. At the moment, most experiments, and in some cases test sites, involve the use of LEDs (light emitting diode) sources.
An example of energy-saving measures implemented to ventilation during refurbishment/upgrading is the installation of jet fans with inclined outlets. It has been shown that these jet fans can enable a significant improvement in the in-tunnel thrust obtained and a reduction in energy consumption.
Outside air quality (at tunnel portals or vitiated air extraction systems) can be improved during refurbishment/upgrading, through increased stack heights or by the installation of vitiated air treatment systems (air cleaning systems). In some countries, vitiated air treatment systems have been put in place (Spain, Japan, Italy, Norway France….). However, after some years of use, the conclusions regarding the efficiency of air cleaning are different from one country to another. The decision to use such systems therefore has to be carefully analysed, taking into account several criteria (investment costs, efficiency, maintenance, etc.).
Finally, tunnel refurbishment or upgrading can provide an opportunity to assist in the preservation of the animal species living around the tunnel. Measures that can be implemented include restoring passageways for certain species or preserving reproduction areas.
General environmental questions related to the design, construction, operation and refurbishment of tunnels are dealt with in the technical report 2017R02EN “Road tunnel operations: First steps towards a sustainable approach”.
Questions relating to the tunnel impact on outside air quality are dealt with in report Technical Report 2008 R04 "Road Tunnels: A Guide to Optimizing the Air Quality Impact upon the Environment".
Tunnel refurbishment or upgrading may require:
If possible, total closure of the tunnel for refurbishment/upgrading is strongly recommended during the entire duration of the works as it undeniably provides the best solution in terms of safety for both workers and users. When possible, it is better to implement closures over short periods and during low traffic (night, weekends etc.).
However, these two solutions mean that a deviation route becomes obligatory and the impact on a given road network can be considerable, especially in urban areas.
Depending on local circumstances, the traffic diversion route may be very long. The risks and costs of a long detour over a short period must be balanced against the risks and costs of a partial tunnel closure over a longer period. It is possible to calculate the costs of detours, including the extra kilometres and delays, to back-up and/or support a decision. Any planned closures must be coordinated in advance with the operators of the roads used for rerouting traffic.
If it is technically possible, if the traffic is low and diversion roads are not practical, an alternate traffic system may enable the tunnel to remain open.
In the event of closure, good advance preparation is essential and can significantly reduce disruption. Regional and/or nationwide publicity in advance of the closure is important (e.g. television, radio, internet, billboards, publication of telephone numbers for information and complaints).
Once the tunnel is closed, diversion signs and signals should be used 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. 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.
When it is inevitable that refurbishment/upgrading work must be carried out while traffic is present, specific traffic management measures must be adopted upstream from and inside the tunnel. In tunnels with two or more tubes, it is possible to close a tube completely and either establish bi-directional traffic in the other tube or establish a deviation route for users of the closed tube. If bi-directional traffic is established in the other tube, there is less inconvenience to users, as they do not have to take a deviation route. However, in terms of safety, this solution is far from ideal (and should be avoided in heavily trafficked tunnels) since it leads to users driving in opposing directions and hence an increased risk of accidents. This risk can be reduced by the use of VMS and overhead lane control signs. In the case of three-lane tubes, the centre lane should, if possible, be kept free of traffic as a buffer safety zone. Additional traffic management measures such as speed limit reductions and the implementation of an obligatory distance between vehicles should also be envisaged.
Where a tube is not completely closed to traffic and simple lane closures are implemented, they should always start before the entrance portal. Traffic should first be merged into the slower moving lane, then moved to the lane available at the incident site before entering the tunnel. In urban tunnel approaches this may not always be possible. Preferably lane closures should run for the full length of the tunnel. A situation where traffic is required to change lanes inside the tunnel is generally not recommended. However, in the case of longer tunnels, it may be advantageous to allow traffic to diverge and use all lanes once clear of all of the work sites. A risk assessment can result in the safest method for the situation.
Once again, additional traffic management measures such as speed limit reductions and the implementation of an obligatory distance between vehicles should also be envisaged.
Addition information on traffic management measures during tunnel closures can be found in PIARC report 2008R15EN: “Urban Road Tunnels: Recommendations to Managers and Operating Bodies for Design, Management, Operation and Maintenance”.
Following construction, the unavoidable deterioration of tunnel ventilation equipment reduces the ability of the system to maintain the required safety and performance levels. In addition, new safety measures may be required for technical reasons or because of changes in the tunnel environment.
Appendix A.5 "Ventilation systems" of the PIARC report 2012 R20 "Assessing and improving safety in existing road tunnels" identifies some examples of weak spots for existing tunnels, explaining why it is often necessary to make modifications to the ventilation systems of existing tunnels, including among others the following:
In addition, chapter 6 "Ventilation" of the PIARC report 2016 R19 "Complex Underground Road Networks", explains the reasons that make the refurbishment of the ventilation systems of the complex networks considerably more complicated than in conventional tunnels and section 3.1 "General aspects relevant for design and refurbishment" of the PIARC report 2008 R15 "Urban Road Tunnels: Recommendations to managers and operating bodies for design, management, operation and maintenance" explains some general aspects that also impact the capacity to conduct refurbishment programs for this kind of infrastructure.