Final Report Lot 9: Public street lighting - Amper

Switching off street lighting after curfew is rarely applied and there are several arguments for
this explained below.
Public lighting requirements are traditionally dominated by road traffic safety concerns and the
perceived security feeling especially in densely populated areas. The absolute reduction of
crime by public lighting is not proven and controversial. There are no large-scale studies
available but it sounds logic that criminality cannot be cured by lighting alone, social control is
also an important factor. But good lighting can lead to higher perceived security and social
activities. Several studies show that lighting can displace criminality from higher lit places
with social control to lower lit places. This is explained by the fact that at low light levels the
eye needs long (typical 5 to 10 minutes) to adapt and some criminals try to exploit this as an
advantage. An opposite criminality shift from poor lit places to well lit places without social
control also seems to be possible. This is explained by the fact that light is simply helpful for
the selection of the crime location and the execution of criminal activities. If no social control or
surveillance is present this lighting will only help criminals.
Switching off 50 % of the lamps in alternating patterns causes bad uniformity in the
illumination of the street, one of the important performance requirements for public lighting,
and is controversial. Partly switching off of public lighting could also cause a criminality
displacement effect as explained in the previous section.
The Expert inquiry (see chapter 2) showed that complete or partial switch off is rarely applied
in the 25 EU-countries, for a maximum of only 5% of the roads.
The lamp survival factor LSF of a discharge lamp is negatively influenced by the number of
switching cycles during its lifetime, due to the high voltage peak that the ignitor generates to
start the lamp. If the number of cycles is doubled, in case of switching off after curfew and
restart in the early morning, the normal lifetime of a discharge lamp is shortened by 30%.
The LSF declared by the lamp manufacturers is based on a test cycle of 11 hours operating and
1 hour off. This cycle approaches the average operating cycle in reality.
If a lamp is switched off and on during the night, the LSF has to be corrected by 0,7 to obtain the
adapted LSF. In this study we apply no correction because partial switch off after curfew is
rarely applied. The impact on savings in electricity consumption in the use phase is directly
proportional to the hours of switch off.
For further calculations we assume 4000 street lighting hours yearly for all road categories.
3.1.3 User and infrastructure influence on energy saving potential by light dimming
Light dimming or light level control can only be used when dimming ballasts are used. This
technology is state of art and will be described in chapter 6 dedicated to best available
technology (BAT). The technology of electronic dimmable ballast is subject of the 'E-Street'
SAVE project on intelligent street lighting.
In general there are four relations that justify dimming according to local conditions:
1. Dimming related to traffic density, e.g. dimming of street light after curfew.
2. Dimming related to local weather conditions.
3. Maximum power point fine tuning adapted to local parameters (e.g.: pole distance, lamp
luminous flux, road reflection, installed luminaire position, shading, .).
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