Equipment and Design Aspects - Road Lighting: Fundamentals, Technology and Application - page 257

Fig. 18.1 Floodlight for
near-horizontal mounting
producing an asymmetrical,
fan-shaped beam

Fig. 18.2 Examples of
external screens or louvres for
floodlights. The floodlight on
the right has an internal
mirror screen as well

with a lower luminous flux can be used in all the luminaires, and consequently these
will exhibit a lower direct upward light component. This advantage is valid in the case
of all luminaires that emit some direct upward light. Needless to say, the reflectance
of the surroundings of the area to be lighted should be as low as possible so as to
limit the amount of light reflected from these surrounds in the upward direction. The
upward flux ratio (UFR) defined in the same Sect. 16.2.1.2, is the metric that allows
us to analyse the situation with respect to different reflectances of the surfaces of the
area.to be lighted and of the surrounding areas.

18.1.4 Lighting Control Systems

Lighting control systems should be employed to ensure that:

• the lighting is on only when needed,

• the lighting is always switched or dimmed to satisfy the lowest requirements pre-

vailing in those situations where the required lighting changes take place according
to time, traffic density, weather, or other circumstances.

Basically, a lighting control system consists of one or more of the following devices:

• input devices: such as switches, timers, photocells, traffic-flow and presence

detectors and weather monitors,

• controlled luminaires: that can be switched or dimmed. In a programmable control

system they should be (hardware or software) addressable,