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Incident detection system safeguards drivers in tunnels 24/7

Published on 13.9.2021

Although tunnels are nothing new, you might still experience a slight clench in your stomach as you drive into the dark mouth of a tunnel or between long rock or concrete walls lit by the glow of artificial lights. Did you know that although tunnels may outwardly appear quite simple, their walls hide a plethora of modern technology that is used to create a real-time situational picture of traffic? Drivers can pass through tunnels with peace of mind, as their safety is being monitored 24/7.

An incident detection system (IDS) will identify any factors that may endanger safety in the tunnel, and will enable planned controls to be deployed in the event of a disruption. The system seeks to ensure tunnel safety, smooth traffic, and a rapid response from the Traffic Management Centre in the event of an incident. The automatic detection and control of incidents also helps traffic to get back to normal more quickly after disruptions.

Control devices indicate when something exceptional occurs in a tunnel

The incident detection system uses a number of control devices that are installed at various points in the tunnel. These devices are used to monitor traffic passing though the tunnel all around the clock. In Finland, these devices will usually be based on cameras and radar. For example, traffic data is collected from the 80,000 plus vehicles that pass through Mestarintunneli on Ring Road I every day, with the aid of 24 traffic cameras, an updated fire alarm system, and 48 incident management cameras.

Incident detection systems are programmed with ready-to-use controls that can be deployed by the Traffic Management Centre when the system detects exceptional circumstances in a tunnel. The most common incidents and hazards in tunnels are caused by fires, large foreign objects, vehicles driving exceptionally slowly or stopping, and vehicles driving in the wrong direction. Reacting as quickly as possible is key in minimising damage.

When an incident is detected, the IDS informs the Traffic Management Centre. The operator will then check the situation and deploy the appropriate pre-programmed operating procedure in accordance with the type of incident. For example, this could mean lowering the speed limit, activating warning, lane-specific or diversion signs, or even closing the tunnel. If the tunnel is equipped with lane-specific signals, traffic can be directed to use only a single lane, so that the entire tunnel does not have to be closed.

When the incident has been resolved, the system can help to ensure that everything is in order in the tunnel before allowing traffic to return to normal. Safety is a priority in tunnels, as they constitute a safety-critical environment that differs from the rest of the road network. Drivers and other road users can also promote tunnel safety with defensive driving skills and by obeying speed limits.

Incident detection systems installed on a case-by-case basis

Although incident detection systems are in use in tunnels all across Finland, their installation is decided upon on a case-by-case basis. Decisions on whether to install an IDS are made at the preliminary design phase, during which the safety concept is created and the monitoring level decided on. A short, straight tunnel with low traffic volumes may not necessarily require an incident detection system.

However, high traffic volumes, multiple lanes, bends or similar features will increase both safety risks and the need for an incident detection system. For example, traffic volumes in Mestarintunneli make an incident detection system absolutely necessary for ensuring safe and smooth traffic.

When a tunnel is opened – either after a new tunnel is completed or an existing tunnel’s systems are renewed – there will be a six-month adjustment phase during which the tunnel’s systems will be tested and optimised. System functionality will be verified using concrete tests that model the kind of incidents that may occur in the tunnel. In Mestarintunneli, these tests were mainly carried out at night in order to minimise disturbance to other traffic while the tunnel was closed for testing.

Future systems will be self-learning and optimise their own operations

In the future, traffic management in tunnels will be able to harness self-learning systems in which the IDS will be able to optimise its own operations in line with traffic in the tunnel. In addition to camera-based controls, it will also be possible to connect the system to new controls based on other technologies. Fibre solutions are an example of some of the latest technology in the field: a fibre cable running alongside a road lane can identify the traffic passing by.

When the tunnel systems in Ring Road I’s Mestarintunneli were renewed and its incident detection system installed, Fintraffic took this opportunity to integrate the tunnel into the TLOIK system, which creates a real-time digital twin of traffic in Finland’s road network. In the future, more tunnels will be added to the system, which supports both Fintraffic’s goal of combining data and services so that travel and transport is as smooth as possible, and its vision of a sustainable and evolving transport system that will be digitised in collaboration with various other operators in the sector.

Jukka Värri, Head of the Infra Construction Unit at Fintraffic Road, was interviewed for this article.