This article describes the specification and development of the specially designed JVT18 luminaire, of which 13,000 are planned for use in the Channel Tunnel. The luminaire and its mountings were required to be resistant to the extreme operating conditions in the running tunnels, over a very long design life. They need to be able to withstand wind speeds of 360kph from all directions and rapid variations of pressure 30kPa above and below atmospheric pressure. Thus an aerodynamic design was developed, to reduce the luminaire's wind cross-section and drag characteristics, and to ensure an equilibrium of forces. Other requirements include: (1) the maintenance of a high degree of tightness; (2) corrosion resistance; (3) ability to prevent water ingress and internal condensation, while water jets clean the exterior; (4) a fixing height of 4.1m above the tunnel walkway, with a spacing of 8m between luminaires. It was found that an 18W twin-limb compact fluorescent lamp with a high-performance long-life reflector would provide the optimal combination of output flux, colour of light, physical size, and life. The design was derived with the help of powerful computer-aided design (CAD) facilities and comprehensive photometric laboratory tests.
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