In order to successfully and efficiently operate and manage a road tunnel, operational tasks and the responsible body for carrying them out, need to be established in order to ensure that all actions required are handled in a consistent and safe way (see page on Operational tasks). The level of safety provided for tunnel users is highly dependent upon the specific characteristics of the tunnel, but it also depends strongly on operational procedures and the people who are in charge of the tunnel.
The people in charge do not necessarily need to belong to the same organisation: stakeholders and roles can be quite different. For example, the traffic police are normally in charge of traffic, but the task is sometimes carried out by a road administration, and in some cases, several tasks are entrusted to a private company/operator. Moreover, the same task (for example: traffic management) can be performed by many different bodies (operating staff, police, subcontractor), so the relative roles and responsibilities have to be specified as well as recommendations to improve the behaviour of people involved in tunnel operation and their level of cooperation (see page on Stakeholder cooperation).
In each case, the organisation of the operation and coordination with all the different bodies must be defined by written procedures and protocols that are simple and straightforward, so that they are clearly understood by all parties and are robust under pressure in emergency situations.
The organisation of operation can be quite different from one tunnel to another; consequently it is difficult to define an overall common framework. However, it is convenient to assess for each tunnel or group of tunnels the most suitable organisation to be adopted both during standard operation and in the event of an emergency situation (see page on Organisation of operations).
Specific organisational and operational procedures are often required for complex tunnels and underground road networks. The following types of tunnels may be considered as “complex”:
All the above-mentioned infrastructures share several similar characteristics:
More information on such infrastructures, with specific case studies, can be found in the PIARC technical report 2016R19EN Road Tunnels: Complex Underground Road Networks.
Moreover, it is essential to establish standard operating procedures as well as minimum operating conditions and emergency plans. This is in fact a key step in planning the operational response to possible tunnel emergencies for which there need to be appropriate specific responses to various types of incidents (see page on Operating procedures).
Ventilation strategies must also be defined from the design stage. Different strategies are possible. The longitudinal strategy consists in creating a longitudinal air flow in the tunnel, in order to push all the smoke produced by a burning vehicle onto one side of the fire. If users are present on that side, they may be affected by the toxic gases and reduced visibility, so the use of this strategy in bidirectional and/or congested tunnels requires great caution. The minimum air velocity for successful smoke control depends on the design fire size and tunnel geometry (slope, cross-sectional area).
The transverse strategy takes advantage of the buoyancy of fire smoke: smoke tends to concentrate in the upper part of the tunnel space, from where it can be mechanically extracted. The system is designed so as to preserve a fresh air layer in the lower part of the cross-section (correct visibility, low toxicity) which allows self-evacuation. It is therefore important to keep the longitudinal air flow as low as possible in the fire region to avoid de-stratification and excessive longitudinal spread of smoke. This strategy is applicable to any tunnel, but the design, construction and operation of the system are more difficult and expensive.
The choice of ventilation strategy is generally guided by fire safety considerations (see chapter 5 of report 05.05.B 1999 "Ventilation for fire and smoke control"
The management and day-to-day operation, as well as the maintenance of a tunnel, involve high operational costs and funding requirements. In fact, tunnels are among the most costly parts of a road network to be operated (in terms of energy requirements, staffing and monitoring). The definition and optimisation of the different cost elements in a tunnel and appropriate recommendations to reduce them have been analysed by the PIARC tunnel committee. The efficient use of energy and the progressive reduction of energy consumption should be considered, with a view to delivering a sustainable operation of the road network (see page on Operational costs).
The final objective is clearly to guarantee an appropriate level of service and quality to the users. The achievement of this objective obviously depends on the nature and overall performance of the facilities and equipment. The performance of the equipment often depends on how this equipment is operated by the tunnel staff in terms of timeliness and appropriateness. Therefore the staff called to perform operational tasks must be well selected when recruited, well trained before starting their tasks and continually throughout their careers (see page on Staff-related issues).
The safety level and the traffic capacity in a tunnel are influenced by changes characterising the road network and the evolution of the traffic itself. The tunnel operator may occasionally need to make minor or major changes to the system or to the management criteria to cope with these changes. It is therefore necessary to monitor changes and accidents using information and feedback, to continuously and systematically improve tunnel operations.
The operator needs to receive feedback from actual operation experiences, which can be analysed and used to propose improvements (see page on Incident Feedback).
When the tunnel equipment no longer satisfies the needs of the operator, the requirements of legislation or when the nature or the level of traffic changes, it may be necessary to upgrade or refurbish the tunnel. For the refurbishment of an existing tunnel, recommendations mainly concerning measures to facilitate the management of the traffic network. Equipment reliability and durability and whole life costs also need to be defined (see page on Maintenance and Refurbishment).
The present chapter essentially concerns tunnels of medium to long lengths, with medium or heavy traffic volume, located in places where prompt external emergency interventions are possible. These tunnels are operated with a specific organisation, dedicated to one tunnel or a group of tunnels, which are part of the same road network.
The page Short / Low traffic tunnels presents the specific conditions concerning short tunnels, or tunnels with very low traffic, or scattered tunnels situated in areas with low population densities.
Generally speaking, tunnels are considered to provide a suitable or even higher level of safety the the open road network, Nevertheless, the potential consequences of incidents (breakdown, accident or fire) may be far more serious in tunnels than in the open air. Moreover, as tunnels are very often obligatory crossing points and are sometimes bottlenecks on the network, each total or partial closure can lead to major traffic disruptions or can oblige users to travel long distances on alternative routes.
For these reasons, operators and road authorities have to ensure the operational continuity and safety of road tunnels. They must guarantee to the users crossing the tunnel a level of service quality and safety complying strictly with regulatory requirements in force.
Figure 1: Maintenance works in a tunnel (France)
Depending on national regulations, tunnel operators and/or traffic police have to manage the traffic in tunnels (and on the route where the tunnel is located). In particular, they need to cater for the safety of users and any staff who may be working inside the tunnel (operating staff, sub-contractors, etc.). In several countries, the traffic police are in overall charge of traffic management and traffic patrolling, while the operator is in charge of operational tasks such as maintenance, operation of tunnel equipment, traffic surveillance and traffic assistance.
Generally speaking, typical tasks for the operators are:
Traffic surveillance and operation of tunnel equipment
Major tunnels (in terms of length, traffic density and complexity of the tunnel) are usually managed from a Traffic Control Centre. Very often, the Control Centre is equipped with remote surveillance systems (e.g. closed circuit television, automatic incident detection) and can remotely control certain equipment (ventilation, signalling, tunnel closure barriers, etc.).
Traffic Patrols
In certain cases, the operator can also deploy patrols that can provide a direct surveillance of tunnel users. These patrols can intervene very rapidly in case of need.
Management of civil engineering works
Civil engineering works in the tunnel undergo regular inspections. There is also regular maintenance of facilities such as drainage systems, gutters and all secondary structures (premises inside the tunnel, technical rooms, etc.),
Management of equipment
In major tunnels, the operator deploys several types of equipment that in the operation phase are under its own control. Tunnels are also equipped with systems that allow the operator to monitor the status of equipment. The operator must cater for the maintenance of equipment fitted in the tunnel. Here again, it is possible to have access to computerised tools to assist in performing this task.
Management of emergency situations
Whatever the nature of the incident, whether it is a problem related to traffic (accident, interlinked accidents, fire, etc.) or to equipment (loss of power supply, malfunctioning of data transmission network, etc.), to intervene or to inform/activate the pertinent service/authority is the standard duty of the operator in charge of the surveillance.
Technical and Administrative management
In addition to tasks directly related to tunnel operation, the operator provides the technical and administrative services supporting the management of the infrastructure and, of course, the personnel. The operator caters for the design of any equipment upgrading, the direction of the works, the investment and operational budgets for the proper functioning of the tunnel. Lastly, the operator also develops statistics and monitors the achievement of its own objectives by preparing periodical reports on the operation of the tunnel/route (financial indicators, traffic indicators, etc.).
The Technical report 05.13.B "Good Practice for the Operation and Maintenance of Road Tunnels" deals with this subject in parts 2 and 4.
The management of road transport is a very complex task. It is even more complex within a tunnel environment. Part of this complexity is due to the fact that skills and competencies required for the management of tunnels are scattered among different services. The cooperation of the different stakeholders is clearly a vital pre-requisite for effective traffic and incident management.
Figure 1: Fire services, tunnel operator staff and authorities during a safety exercise
The Technical Report 2007R04 "Guide for organizing, recruiting and training road tunnel operating staff" defines the organisational tasks in a more precise manner.
Although the organisation of tunnel operations varies from one country to another, generally it involves the following groups:
In a few cases, emergency rescue services are considered as part of the operating staff.
In some cases, a single organisation can be responsible for all the personnel required for tunnel operations. In other cases, operations may be shared by several public and private organisations. For example, the tunnel owner or the road administration may entrust a public or private organization with operation as a whole and then contract out specific operational tasks (e.g. maintenance tasks).
Incident management measures depend on national regulations and local requirements specific to each tunnel. Consequently, the organization of the operator and the traffic police depends on the local context.
Technical Report 2007R04 defines the organisation of operation in greater detail in chapter 4 "Operating staff: tasks and facilities".
The operation of complex tunnels and underground networks must take into account specific factors and in particular:
The volume of traffic is generally a more significant factor and in high traffic volume conditions traffic congestion is much more frequent. It follows that the number of persons in the tunnel is much higher and in the event of an incident, the number of users to evacuate will be more significant.
Ramp merge and diverge areas are important locations in terms of risk of accidents.
The assumption, which is sometimes prevalent from the start of projects, that there will never be a traffic blockage must be analysed with much circumspection. It is indeed possible to regulate the volume of traffic entering into an underground network in order to eliminate all risk of bottlenecks. Nevertheless, this leads to a significant decrease in the capacity of the infrastructure (in terms of traffic volume) which often goes against the reasoning that justifies its construction. Over time, measures of reducing entering traffic must be relaxed, or even abandoned because of the need to increase traffic capacity. The probability and recurrence of bottlenecks increase, disregarding the initial assumption upon which the network was based (particularly in terms of safety and ventilation during incidents).
Issues to take into account include:
Ventilation systems in complex tunnels and underground networks must take into account:
Communication with tunnel users must be reinforced and adapted throughout the multitude of branches within the network. Communication must be able to be differentiated between the different branches according to operational needs, especially in the case of fires.
Users must be able to identify their position inside the network, which would require, for example, the installation of specific signs, colour codes, etc.
Directional signs and prior information signs at interchanges or ramps must be subjected to careful consideration, particularly the visibility distances with regard to signals and the clear legibility of the signage.
Attention must be given to the interfaces and cooperation between stakeholders, notably for traffic management matters and safety matters (especially fire incidents), including evacuation of users and intervention of emergency response agencies in response to fire incidents.
A complex underground network is usually operated by numerous operators whose cultures, skills, objectives and organisations are multiple and often different. However, the safety conditions inside the network and the level of service provided to users require good coordination between all the operators, together with excellent mutual understanding and confidence.
A Coordination Committee with a strong leadership is therefore absolutely essential.
Control centres must take account of the interfaces within the network and between diverse operators. They must allow the transmission of common information which is essential to each operator, and facilitate the possible temporary hierarchy of one control centre over another. The architectural design of the network of control centres, and of their performance and methods, must be subjected to an overall analysis of organisations, responsibilities, challenges and risks. This analysis should reflect a range of operational conditions such as during normal and emergency scenarios and should review the interaction between the different subsections of the network and the respective responsibilities of each control centre.
The safety conditions of a complex underground network do not differ fundamentally to those of a standard tunnel. However, everything is more complex, due to:
Excellent knowledge of the networks and the conditions faced within the network during an emergency are therefore absolutely essential. Certain tools may be helpful, such as:
However, although these tools are necessary, they will never replace training and basic human factors such as the capacity for initiative and adaptation which remain fundamental for coping with a large-scale event.
Every tunnel operator produces and updates written procedures (sometimes called "Operating instructions") which define the objectives and criteria of possible actions by different internal service providers, which can affect the tunnel or road. All types of operational events need be taken into consideration for the procedures, including routine incidents, serious accidents and emergencies. The "Operating instructions" contain the basic actions to be carried out with associated procedures and existing constraints.
The operator's staff also needs an emergency plan for both intervention after a road accident and technical failure of equipment in the tunnel. This plan usually meets regulatory requirements and includes operational procedures and instructions involving, at minimum, the tunnel operators and the intervention personnel in case of an incident or technical failure. The emergency intervention procedures should be coordinated with those applied by emergency and rescue services. The detailed content of this plan could be defined by national instructions or directives specific to each country and needs to be tailored to the specific technical and organizational aspects of the tunnel.
Technical Report 2007R04 defines the organisation of operation in greater detail in chapter 4 "Operating staff: tasks and facilities"
The tunnel ventilation system should ensure adequate air quality during normal operation and maintenance activities, as well as providing the desired smoke management in case of fire. Moreover, the escape routes should be kept free from smoke.
However, when selecting and operating a ventilation system, normal operation and smoke management cannot be considered independently.
During normal operation, it is required to keep the pollutant level inside the tunnel below defined threshold values for visibility due to particulates, or toxic gases in each section of the tunnel. Some tunnel ventilation systems can be primarily designed and operated in order to minimize the impact on the environment at the tunnel portals. Further information on design criteria for normal operation can be found in the specific section of the page on "Design and dimensioning".
Control for normal operation should be achieved at minimal operating costs. It is conventional to control the operation of the ventilation system through measurement of the relevant pollutants (including opacity and either or both CO and NOx), to optimise the use of the system. In some cases, tunnel operators need to use SCADA systems to check the proper functioning of automatic control systems. For further information see the page on "Control and Monitoring".
Other objectives are occasionally pursued e.g. to minimise the risk of condensation occurring on the windscreens of vehicles and preventing the entrainment of fog from outside the tunnel. For maintenance work in the tunnel, the tunnel ventilation has to ensure the air-quality criteria for longer exposure of workers.
In case of a fire in a tunnel, the ventilation system must be operated in order to establish and maintain appropriate conditions for self-evacuation and rescue operations.
During the self-evacuation phase (also called the self-rescue phase, during which tunnels users would, of their own volition, attempt to evacuate from the tunnel), the ventilation system aims to create and maintain a tenable environment for the evacuation of tunnel users. Specifically, this environment consists of acceptable visibility and air quality levels.
During the fire-fighting phase, the ventilation system operation has to be decided by the head of emergency operations, who should choose the best solution taking into account the possibilities of the ventilation system and the operational needs of the firemen.
Further information can be found in section 8.3 "Operation of smoke control systems" of the PIARC report 2007 05.16 "Systems and equipment for fire and smoke control".
In contrast with normal operation, where conditions in the tunnel change rather slowly, the conditions during a fire may change rapidly, leading to deteriorating conditions within the tunnel. The designer initially defines the objectives of the ventilation system, sizes the necessary equipment and proposes what actions the operator should take under various scenarios. The designer, therefore, needs to understand the behaviour of the smoke, what the tunnel user might do (human behaviour), and what the operator, and later emergency services, should do in response to an emergency.
Different ventilation strategies may be used in tunnels. The choice between them is generally guided by fire safety considerations; the use of the system in normal operation is adjusted to suit.
The PIARC report 1999 05.05 "Fire and Smoke Control in Road Tunnels" provides extensive details on smoke management and PIARC report 2011 R02 "Road tunnels: Operational strategies for emergency ventilation" discusses different ventilation methodologies and operational strategies..
For tunnel operators this is reflected in a series of choices that can be made about the configuration of existing ventilation equipment. Usually these choices are based upon pre-planned equipment usage configurations, hence the following questions are to be considered:
The objectives of the design should provide a useful means of characterizing the potential operational performance of the ventilation system, whereas the actual characteristics of the system define the achievable result from an operational perspective. In responding to a real incident this distinction may be critical – and the importance of the design-operator interface crucial.
In addition, it is essential to establish standard operating procedures for road tunnel fires. The development of an integrated Emergency Response Plan is an essential first step in planning the operational responses to tunnel emergencies. The plan should specify particular responses to various types of incidents, including the description of how the ventilation system should be used. For its preparation, a proper coordination and interaction between the tunnel designers (in some cases), the tunnel operators, and all outside agencies that might ultimately become active responders to an emergency incident within the tunnel, is required.
In the case of urban or complex underground systems, tunnel operators have to face additional challenges: during normal operation to properly control the fresh air flow inside the tunnel and make sure that all branches can received the required amount of air for pollutant dilution; and in case of incidents with fire, to minimise the harmful effects of smoke by isolating different tunnel sections to avoid smoke contaminating the whole tunnel network.
Further information on main issues related to ventilation of these tunnels can be found in chapter 6 "Ventilation" of the report 2016 R19 "Road Tunnels: Complex Underground Road Networks".
Experience shows that a kilometre in a tunnel is always more costly than a kilometre of the same road outside. Underground structures require systems and equipment that ensure safe operation under normal operating conditions and allow the protection and the evacuation of users and the intervention of rescue services in case of an incident, accident or fire. These facilities not only involve considerable investment costs but also result in particularly high costs for operation and maintenance. Thereby the role of the operator is to ensure the continuity and the safety of operation in a context of controlled costs.
In all cases, even a high standard of tunnel operation may not allow an optimisation of operational costs, if the design and the construction of the tunnel have been undertaken to a low quality level. Operational costs therefore need to be a major consideration during the different phases of the project and the work execution. Solutions need to be found well before becoming an issue during the operational phase.
Operational activities have to be organised at an adequate level in order to ensure that the expected lifecycle of the equipment is met, without compromising mandatory operational performance requirements. The lifecycle of equipment in tunnels is normally shorter than in other environments, since the atmosphere in tunnels is particularly corrosive.
The Technical Report 05.06.B "Road Tunnels: reduction of Operating Costs" is entirely devoted to operating costs and in particular focuses on how to reduce them.
Tasks entrusted to the operating staff are essential for safety and the overall efficiency of tunnel operation. Moreover, the context is evolving, with operational issues growing in importance and operating systems becoming increasingly complex.
Figure 1: Operating staff in a tunnel control centre (Spain)
The staff in charge of tunnel operation therefore need to satisfy the following requirements:
During recruitment phases, the qualifications required for the future operators must be defined according to the nature of operational tasks. Even if the tasks are similar in all countries, the people responsible for executing them do not necessarily belong to the same kind of organisation in each country. Nevertheless, the skills and aptitudes required should be similar.
While designing the staff training (initial or permanent), the following two issues need to be addressed:
If there are no national rules on the content of training, the operating body has to adapt its training programme to the specific characteristics and requirements of its tunnels.
The Technical Report 2007R04 "Guide for organizing, recruiting and training road tunnel operating staff" specifies the recruitment and training of personnel in greater detail, chapters 7 "Recruitment of operation staff" and 8 "Training operating staff" .
The operator needs to regularly test procedures and the efficiency of personnel, making sure that staff are familiar with the different equipment installed in the tunnel. Any possible deficiencies in the execution of specific tasks can thus be detected.
In addition to internal exercises, the operator and emergency services need to organise joint rescue exercises with the participation of the traffic police, the operator, medical services and the fire and rescue services. The results of each exercise should be analysed. If lessons drawn from an exercise reveal any shortfalls, the intervention strategies should be reviewed.
For road tunnels, exercises should be regarded as an integral part of the tunnel emergency planning process. In many countries, road tunnel safety regulations specify the time intervals between emergency exercises and sometimes give some indication about the contents of the exercises.
For tunnel operators, organising such exercises represents a considerable task.
The collection of data regarding incidents and accidents and their analysis is essential both for the evaluation of the operation criteria and for the assessment of risks in the tunnel. All of this is important with a view to a continuous improvement in tunnel safety. In particular, the collected data enable the frequency of events to be evaluated. Data also provide feedback regarding the consequences of events and also the effectiveness of safety measures and equipment. They also provide additional information on the real behaviour of tunnel users.
The collection and analysis of data regarding incidents and accidents should allow the following two objectives to be achieved:
Lastly, they provide information (national statistics according to the type of tunnel) that is useful for the analysis of risks relating tunnels that are in project stage (ie. in development) or tunnels under operation that do not yet have an adequate database.
The lessons drawn from the operation, particularly during incidents and accidents, should be analysed. In fact if the results of these analyses reveal deficiencies, there is an opportunity to intervene by improving strategies and/or operating instructions.
The Chapter 3 "Collection and analysis of data on road tunnel incidents" of Technical Report 2009R08 defines in detail the conditions for analysing data from incidents and/or accidents.
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.
Fig 1 : Short tunnel with lighting in rural area
For these particular tunnels, it is recommended to carry out a detailed specific analysis for each tunnel (or group of tunnels located on the same road network), taking into account:
This analysis will then make it possible to organise and to implement the most suitable operating system, according to the specific conditions of these tunnels.