TRILUX Luminaires - Proljus AB

Energy efficiency
350
Vehicles per traffic lanes
700
600
500
400
300
200
100
0
19:00 20:00 21:00 22:00 23:00 00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00
Time
2.8 Schematic diagram of the classic half-night lighting system (blue) and a fine-tuned
adjustment (green) of the lighting level to the traffic volume (red) measured for a major
inner-city traffic road. The area above the green or blue curves represent the potential
savings.
Switching times
Bearing in mind the scientifically proven
decrease in traffic accidents in case of good
road lighting, it is irresponsible to reduce the
road lighting or even to switch the luminaires
completely off in sections in order to cut
energy costs. Switching off individual light
points in particular creates an additional
danger, since this results in camouflage
zones, in which motorists cannot recognise
danger sources.
Lighting level 100 %
50 %
It is better to adapt the lighting level to lower
traffic flows during less busy times, e.g. by
half-night lighting or reducing the wattage of
lamps, which is also permissible according
to the relevant standards.
High-pressure discharge lamps can be
switched to a lower wattage, thus resulting
in a decreased luminous flux, by increasing
the impedance of the ballast. For less
demanding requirements for the lighting
level, e.g. at times when there is little traffic,
this is a way to save energy without worsening
the lighting uniformity, which is of major
importance for traffic safety. The wattage can
be reduced using a ballast with a separate
tap or by means of separate extra impedance.
Switching is implemented by means of
a relay and a separate control phase.
The following energy savings can be achieved
by reducing the wattage of the lamps (halfnight
lighting):
• Approx. 23 % from 10 p.m. to 6 a.m.
• Approx. 20 % from 23 p.m. to 6 a.m.
• Approx. 18 % from 23 p.m. to 5 a.m.
If the lighting level is adapted to the flow
of traffic in suitable steps, it is possible to
reduce energy costs by up to 40 % (fig. 2.8).
The activation and deactivation times and
thus the time the lighting installation is
operating have a significant influence on the
energy costs and lamp replacement costs.
In work places, the switching times are
based on the work-related necessity for
lighting and the regulations for on-the-job
safety. For accent lighting of public buildings,
the switching times are determined by taking
into account representation factors and cost
expenditure.
Example
A major traffic road with an average daily
traffic volume of less than 25,000 vehicles
must be illuminated during the periods of
rush hour traffic with the mean luminance
of 1.0 cd/m 2 in accordance with EN 13201
(lighting situation A3, lighting class ME 3b).
At times when there is little traffic, for instance
10 p.m. and later, the volume of traffic
falls, e.g., to less than 15,000 vehicles. As
a result, the complexity of the visual field
and the difficulty of the driving task also decreases.
For this purpose, the lighting class
ME 5 with a mean luminance of 0.5 cd/m 2
could be applied and the lighting installation
switched to half a level (half-night lighting).