CNA Tunnel

The Contournement Nord d'Angers (CNA) tunnel is part of the A11 motorway that bypasses the city of Angers. This twin-tube, two-lane tunnel was built to facilitate traffic flow between Nantes and Paris. The lighting in the tunnel was provided by 1,068 PF5 luminaires installed in 2008. Cofiroute, the concessionaire and operator of the tunnel, wanted to upgrade the lighting to LED technology as part of its sustainability commitment to reduce energy consumption and improve uniformity in the tunnel. 
 

Retrofit LED kit for luminaires in excellent condition

The PF5 was developed over 20 years ago to resist corrosion in road tunnels. It has an IP 66 rating to guarantee the reliability of the luminaire's photometric and electrical equipment. 

After more than 15 years in service, the luminaire bodies were still in excellent condition. Cofiroute, which is committed to sustainable lighting solutions that preserve resources and reduce its carbon footprint, wanted to upgrade the lighting to more energy-efficient LED technology.

Originally designed for discharge lamps, the PF5 is ideal for retrofitting with LEDs to deliver a higher light output using less energy, lower maintenance costs, reduce carbon emissions and contribute to a more circular economy. By choosing to retrofit the PF5 luminaires in the tunnel, rather than replace them, Cofiroute is able to keep the original luminaires in excellent condition, junction boxes and distribution network, minimising waste and reducing its carbon footprint, while improving the quality of light and energy efficiency.
 

Optimised tunnel lighting design to ensure safety

The right lighting design is essential for a safe tunnel. We redesigned the tunnel lighting installation, calculating the number of luminaires and their orientation to create a curve as close as possible to the CETU (French Centre for Tunnel Studies) normative curve for an efficient and economical installation. Using our high performance LED optics, we were able to reduce the number of luminaires needed to light this 1.7km tunnel to 925, further reducing energy and maintenance costs.

Due to the high volume of traffic passing through the tunnel, we strategically increased the number of luminaires at the tunnel entrances to avoid the "black hole effect" and to ensure an easy and comfortable transition in the critical zone.

Now equipped with the latest generation white LEDs, the PF5 luminaires deliver a crisp bright light with exceptional colour rendering to optimise the visual perception of drivers, highlighting any potential obstacles and increasing security in the tunnel.
 

Quick and easy installation for minimal disruption

To minimise disruption to traffic, the refurbishment was scheduled to take place over 10 nights between August and October 2024. The first night was dedicated to validating the ‘calculated’ lighting levels and identifying any potential challenges in the deployment process, while ensuring that the tunnel was reopened at 6am in time for the early morning traffic.

Lesens EREA (part of the VINCI Energies group), the contractor for this major project, had to clean the exterior of the PF5 luminaires, disconnect and then remove the old lamps and reflectors, install the LED retrofit kits and reconnect the 925 luminaires (with the tunnel reopening every morning). At the same time, the control circuits were adapted to the three lighting modes in the new photometric study, all the circuit breakers and electrical protection devices were replaced to absorb the high current requirements at start-up (0-crossing technology) and the additional retrofitted PF5s were installed at the tunnel entrance to comply with the CETU curve (reusing the housings removed from other parts of the tunnel).

Thanks to the excellent teamwork between the different partners and the ease of installation and connection of the retrofit LED kits, the work was carried out quickly and efficiently to meet the deadline.
 

Over 50% less energy and less carbon

A total of 1,068 PF5 luminaires fitted with high-pressure sodium lamps ranging from 100 to 400W (with an average power of 269KW) lit the tunnel. As part of the new tunnel lighting design, 925 luminaires were retrofitted with LED optics with an average power of 130KW.

The energy efficiency of these LED retrofit kits has reduced the total power of the installation by more than 50%, significantly reducing the energy consumption.
 

Supporting a circular economy

By conserving the existing luminaire bodies, which were in excellent condition, Cofiroute has minimised the resources and energy needed to relight this tunnel, contributing to a more circular economy. The remarkably clean interior, despite the challenging tunnel environment, highlights the effectiveness of the luminaire design. The optics have been completely protected from dust and dirt and will provide consistent, reliable long-term performance.

We are delighted to contributed to ensuring a safe, comfortable and sustainable CNA Tunnel that will serve the community for many years to come.