OPTEX Security: Securing Europe’s tunnel network

Tunnels are vital to Europe’s transport infrastructure, writes Dale Jones, Project Sales Manager, UK and Ireland, OPTEX Security EMEA.

Tunnels speed up the transit of goods and people by rail and road, carry communication networks, connect communities and contribute to the overall economy and competitiveness of the European Union.

Governments and businesses are far more concerned today about keeping them secure and, as tunnels have become more complex, so too has the technology to protect them. 

More transport systems are being built in underground tunnels each year in order to reduce the effect of noise and pollution on people’s lives and the environment.

Those tunnels are also getting longer and deeper: HS2, connecting the north of England to the south, has sections that are 90m below ground in places; and the Brenner Base Railway Tunnel from Innsbruck, Austria to Fortezza, Italy, is 55km through the Alps (Construction Briefing). 

These tunnels are vital because without them some European economies may falter. The Alpine network, for example, carries more than 220 million tonnes of goods every year.

When the Mont Blanc tunnel closed after a fire in 1990, Italy lost an estimated €300m to €450m per annum until it reopened three years later and incredibly, when the Frejus tunnel closed in 2023, logistics companies spent an additional €10,000 per journey re-routing deliveries through Switzerland (UIRR).   

Whilst such large-scale incidents are rare, smaller ones are not. The EU Railway safety statistics reveal there were 1,567 significant railway accidents in 2023 with 841 lives lost and 569 people seriously injured (Eurostat).

Over half (58.4%) of fatalities were trespassers – typically vagrants (setting up tents in tunnels), vandals or graffiti artists.

Even if there is no injury or loss of life, vandalism, for instance, can cause derailments, collisions and fires, all of which are costly.

In one year alone there were 3,559 acts of vandalism and graffiti, on Spanish railways, of which 729 attempts were stopped. Such incidents cost Spanish Renfe roughly €25 million annually (Railway Supply). 

The Austrian train operator ÖBB spends €3.2m, and Brussels’ SNBC, around €6m cleaning graffiti off rolling stock and in 2022 (The Brussels Times), Brussels SNCB suffered 147 incidents of vandalism, with a price tag of around €1.12m (Global Railway Review).

These incidents are not as economically damaging as the Mont Blanc fire but show that protecting the railways and the trespassers is expensive, and it isn’t easy. 

Tunnels are enclosed, dark and damp, making it difficult for train drivers to see trespassers who have nowhere to escape.

Accurately detecting a person in the confines of a tunnel is challenging enough by itself and is only made more difficult when several trains are using the tunnels at the same time. 

Upgrading CCTV to protect tunnels 

For around 50 years, CCTV has been used to monitor tunnel entrances and exits. But early systems needed security teams to constantly watch between 12 to 24 camera feeds on a single screen.

After two hours, their attention began to wane and the risk of missing incidents rose. 

Thankfully, video analytics, or video content analysis, was created and overcame some of these challenges.

Now, camera sensors with advanced algorithms process digital video signals in real-time and transform them into intelligent data.

A trespasser will instantly trigger an alert which directs the security teams to the appropriate feed, who can then immediately decide what action to take.  

The technology, though, has to keep evolving. Trespassers with intent are becoming more sophisticated. They have learnt that they can go undetected by moving towards or entering the tunnel as the train is passing or deliberately altering their appearance to fool the analytics software. 

The heat and humidity inside tunnels can adversely affect many technologies, and radar or microwave technologies struggle to filter the noise and false alarms generated by the train – thus failing to provide adequate detection. 

Modern laser detection sensors are unaffected by humidity or lighting conditions. They can work in complete darkness, strong sunlight and artificial lighting, and are unaffected by the train’s headlights, the reflections on tunnel walls or other trains passing through.

Equipped with sensing analytics, LiDAR technology is not reliant on visible light or thermal spectrums, which is useful when tracking a person or animal from the lit tunnel entrance to inside and along the tracks or in the shadows. 

Accurate detection 

More advanced detection sensors, such as OPTEX’s REDSCAN series, use dynamic event filtering to accurately identify human trespassers.

When monitoring a tunnel entrance, detection criteria or logic is applied to establish different detection zones, the sequence of alarm triggers and the size of an object, which in combination can determine whether a train, a person or a group of people is entering the tunnel.  

If a train is detected, the system will stand down. If a person or group is detected, the control centre and train driver are alerted, allowing the train to slow down or stop to prevent an accident.

These LiDAR sensors can detect objects across eight different zones and an area of 100m. They can be configured to recognise objects larger or smaller than a defined size; for example, they can ignore trains while detecting people or overlook small rocks but identify boulders. 

Additionally, the sensors can determine the precise X/Y coordinates of any detected object or objects, enabling tracking when integrated with advanced VMS software.

As part of an advanced Track Intrusion Detection System (TIDS), which integrates multiple technologies, these sensors facilitate the intelligent tracking of individuals’ movements, allowing security operators to monitor them and pinpoint exactly where they can be apprehended. 

Deep inside a long tunnel, security systems must also overcome the effects of increased pressure and pollutants.

Train tracks, when cleaned, throw up a considerable amount of metal and oil into the air, which, like pollution from diesel fumes, can coat or potentially damage the cameras and sensors.  

Dirty cameras or sensors cannot detect intruders or incidents, so they need to be cleaned. REDSCAN sensors feature an algorithm that continuously measures the return or reflection of the laser signal, tracking the percentage of the unit’s window that is soiled.

Once a certain level of soiling is reached, security personnel are notified.  

OPTEX has also developed a special self-healing foil for laser sensors used in underground tunnels, which protects the laser window from dust, metal fragments, oil and other pollutants.

Sensors are often adapted for different environments and various uses, so the correct choice of sensor is essential to the design of any tunnel security system.  

Designing the right system 

Designing a tunnel security system begins with a survey of the site and an estimate of how many cameras and sensors are needed for the size of the tunnel to ensure sufficient coverage. 

Assessing the types of incidents needing detection, such as graffiti artists, vandalism, terrorism or trespassers and animals wandering onto the tracks, is also crucial.

The quality and amount of light at the openings and along the tunnel will help determine whether dynamic filtering functionality is needed because they will be unaffected by trains passing or light bouncing.

All this allows the system to be configured for early, accurate detection that prevents incidents whenever possible. 

Ultimately, finding the right solutions and combination of technologies that are fit for purpose will vary from tunnel to tunnel.

But, continued development and the advancement of new technologies can only help enhance safety and ensure Europe’s critical tunnels remain open.