The Zheleznitsa Tunnel is the longest road tunnel ever built in Bulgaria. Just over 2km long, it is located on the Struma motorway which connects six of the largest cities in the western part of the country and is also part of the E79 motorway that runs from Miskolc, Hungary to Thessaloniki, Greece. As such, it is strategic for the regional development of Bulgaria and the bordering countries, providing a direct route through Bulgaria to the Aegean Sea and alleviating traffic congestion in neighbouring cities.
The tunnel opened in December 2022. It is equipped with the latest state-of-the-art systems – ventilation, fire alarms, CCTV, traffic management, audio systems to ensure the safety for all drivers and passengers. Naturally, the local authorities wanted an advanced lighting solution that would guarantee the safety and comfort of all motorists and passengers driving through the tunnel while minimising energy costs.
Modern tunnel LED lighting
The GL2 COMPACT, which has proved its worth in tunnels worldwide, from Sydney to Medellin, was chosen to provide the base lighting. Just over 200 GL2 COMPACT 4 luminaires were installed in two continuous lines in each of the 2 tubes. They ensure high uniformity on the road and provide a bright white light, which ensures perfect visibility and comfort for drivers, making them feel as safe as on an open road.
Optimised safety for tunnel entrances
As tunnel entrances are particularly critical zones due to the contrast with natural daylight, a luminance meter was installed at each tunnel entrance and the OMNISTAR was chosen to provide the reinforcement lighting.
Throughout the day, the luminance meter calculates the amount of light needed for the entrance zones; the more daylight there is outside the tunnel, the higher the level of light inside the tunnel will be to help drivers quickly adapt to the tunnel environment.
Just over 80 energy-efficient OMNISTAR luminaires have been installed in parallel with the GL2 COMPACT 4 fixtures in each tube to ensure an easy and comfortable transition by reducing the contrast with natural daylight.
BTS: smart tunnel lighting to optimise efficiency
All of the tunnel lighting luminaires are managed by the BTS control system. It adapts the light levels according to external conditions (luminance measurements performed by L20 cameras), and provides a number of predefined lighting scenarios, from 100% to night-time. The different lighting scenarios and adjustments of the luminance levels on a daily basis ensure that energy consumption is reduced to the minimum required.
The BTS lighting control system can be integrated into the operator's SCADA platform via the MODBUS TCP protocol, allowing the SCADA operator to remotely control and monitor the tunnel lighting from the control room at any time.
Performance over time
Both the GL2 COMPACT and OMNISTAR luminaires are made of sturdy materials to protect the LEDs from the highly corrosive and humid tunnel conditions and to guarantee performance for many years to come. Thanks to their strong composition, maintenance operations will be spread out over time, avoiding unnecessary interventions and costs.
The local authorities are pleased with the modern and sustainable tunnel lighting solution. It ensures safety and comfort for tunnel users while reducing energy costs and carbon emissions.