Tunnel intelligence

By Iskra Sistemi

Works have been completed in another of the Slovenian tunnels – the Šentvid tunnel. As its final opening has been eagerly anticipated, the completion times were very short and corrections are still being dispatched.

Difficulties in connection with the selection of the main contractor, long-lasting procedures before signing the contracts, introduction into the works and other difficulties caused the works to start no earlier than in the spring of 2008, yet by 30 June 2008 the majority of works had been completed.

Control and Monitoring System
Iskra Sistemi is equipping the tunnel with the control and monitoring system, i.e., the most intelligent part of the tunnel electric safety equipment. The basic elements of the system are local stations built in the emergency call niches and sub-control tunnel centres and the system is completed by control computers and software in the Smodinovec Control Centre from which the Šentvid tunnel is managed.

All systems are integrated by the control and monitoring system which enables the personnel on duty in the traffic control centre a clear view of the events and traffic flow through the tunnel as well as of the state of all systems installed in the tunnel.

Due to specific traffic conditions in the tunnel which may cause traffic accidents with unforeseeable consequences it is essential for the personnel on duty, who supervise the tunnel around the clock, to have a complete overview of all subsystems as well as a possibility of taking prompt and efficient action.

Basic tunnel control level
Basic tunnel control level consists of local controllers, which are modular microprocessor control systems of MSKE60 group. Upon the user programme commands, they are capable of performing various logic, sequential, time, count, arithmetic, regulation, and communication functions. Local controllers of the same type are used in the tunnel control systems of all Slovenian tunnels (Trojane, Podmilj, Kastelec, Dekani, Jasovnik, Ločica, Golovec, Pletovarje, Golo Rebro and Karavanke), and they are also used in the motorway and urban traffic control systems, ABC lanes of tolling plazas and border crossings.

Control of electric and mechanical tunnel equipment
Local controllers are connected with communication links to all subsystems, collecting data from them and automatically controlling them depending on the prescribed control algorithms. The Šentvid tunnel subsystems comprise traffic lights, blinkers, variable message signs and LED indicators, traffic counting by inductive loops, emergency call and SOS buttons, CO and visibility measurements, wind velocity and direction measurements, anti-burglary protection, tunnel illumination, video surveillance system, and automatic detection of traffic queues, stopped vehicles or vehicles driving in the opposite direction, fire alarm, low-voltage and middle-voltage equipment control, uninterrupted power supply system, fire-fighting water reservoir control, wastewater control and hydrant water heating, radio equipment and tunnel ventilation.

Upper tunnel control level
In normal operation mode all control sequences in the tunnel are executed automatically. The operator in the control centre only monitors the events and takes appropriate action if necessary. In addition to the main control computer, the system contains a stand-by computer at sub-control location. Both computers are interconnected into a network so that in addition to the supervision from the main control centre the tunnel can also be managed from the sub-control centre. The supervision from stand-by PC is also used, if the communication between the tunnel and dislocated control centre is interrupted.

The PC control centre systems equipment and software executes and enables the following functions: reception and analysis of processed data from all subsystems in the tunnel, additional data processing, real time data base, display of data, information and alarms via graphic terminal, dialogue with operator, events printing, archiving, on-line modification of data and parameters, suitable data protection and off-line modification of algorithms.

The PC control system consists of computers of industrial design, colour screens, colour and matrix printers, TV system operating console, radio links operating console, TV monitors and video wall.

Functionally clear and maximally reliable concept of control
Iskra Sistemi uses a functionally clear and maximally reliable concept of tunnel control. The concept used is incomparably more adaptable than systems which have autonomous controllers for individual subsystems with a single data concentration point. In the event of a failure or interruption of communication with a local controller the entire control system continues to operate normally except for the small part of the tunnel covered by the failed local controller.

Safety first
All the subsystems are important for controlling traffic through the tunnel. A mere pedestrian stepping into the tunnel or opening of doors in a tunnel niche causes speed restriction and activation of blinkers. Any greater danger – e.g., detection of a fire, a stopped vehicle or a vehicle driving in the opposite direction, excessive concentration of CO in the air – can cause the tunnel to be closed. In addition to automatic tunnel control algorithms, the operator monitoring the tunnel by means of surveillance cameras can intervene at any moment.

There is actually a lot of equipment in the tunnel, although you only notice traffic signs, illumination and fans when passing through, while the most important system taking care of tunnel control and safety is hidden from the eyes of the drivers. Yet it depends on the tunnel control system whether the equipment installed will detect any hazard in the tunnel in time – and react properly. The very speed and correctness of reaction are what the safety of the Šentvid tunnel depends on. If the installed system saves human lives, our job has been done well. And this is just what happened already on the first day of the tunnel’s operation.