Civil Engineering Reference
In-Depth Information
Fig. 22.2
Example of a
longitudinal LED
tunnel-lighting luminaire
why many tunnels make use of tubular fluorescent lamps for the interior zone. Solid-
state LED light sources combine a high efficacy and extremely long life and can also
be produced in long linear versions by mounting multiple LED points in a long flat
or round shape (Fig.
22.2
). LEDs permits the development of flat luminaire shapes
so that the lighting will call for less space in the tunnel. The installation costs with
such compact luminaires are reduced as well. Thanks to solid-state technology, the
LED is also a robust solution that can withstand a tunnel's hostile environment with
greater resistance to shock and vibration than can conventional solutions. LEDs can
be instantly switched and easily dimmed to accurately suit varying daylight and night-
time conditions. This means that overlighting is avoided and energy consumption is
reduced. Also, the extremely long life of LEDs reduces both initial and maintenance
costs.
Gas-discharge and solid-state lamps cannot function properly when they are op-
erated directly from the mains-supply voltage. They need control gear to ensure that
the lamp can be started (gas-discharge lamps); that it can be operated stably over a
longer period; and, if the lamp type permits of it, that it can be dimmed. The control
devices needed are called igniters, ballasts and dimmers. The electrical control gear
employed with solid-state lamps is usually referred to as a driver. Section 10.4 of
Part 1 gave detailed information on electrical gear.
22.2
Luminaires
The general aspects of outdoor luminaires are dealt with in Chap. 11 of Part 1 of this
topic. Here we shall describe specific aspects of tunnel-lighting luminaires.
Tunnel-lighting luminaires can be divided into two groups according to their
light distribution in a vertical plane parallel to the tunnel axis: symmetrical and
asymmetrical luminaires. Those in the latter group are employed when counter-beam
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