ingineria iluminatului - Journal of Lighting Engineering - Prof. Florin ...

one should look for alternatives to enhance
the visibility of visual tasks other than by
“more light” only. There are for example
traffic situations that are so complicated
and confusing that a lot of light is needed to
enable the driving task. Of course, a better
alternative than “more light” is to simplify
the complexity the driver has to deal with.
Dynamic road markings (e.g. LEDs built
into the road surface) to visually simplify
complex situations without (extra) road
lighting, is another example of applying the
visual ergonomics concept.
Where lighting
It is not the lighting expert who should
determine in which areas road lighting
should be present. That is a decision where
politicians should play a decisive role on the
basis of arguments such as cost-benefits,
importance of crime prevention, importance
of promotion and importance of giving
identity to an area. If chosen for lighting the
lighting designer is responsible where the
light in the space should be. We discussed
already about luminance of the road surface
and thus horizontal illuminance, semicylindrical
illuminance on face height or
half-spherical illumination at ground level. It
seems important that the lighting has a threedimensional
component. Here, a statement
of the Dutch lighting expert Joh. Jansen in
1956 published in International Lighting
Review is especially today relevant [11]:
”A city street with dense motorized and
pedestrian traffic is not much else than an
elongated room. Just as in a factory hall,
that street will have to receive light as to
enable people to see quickly and distinctly
Road lighting in the light of the future
what is happening. This no longer has
anything to do with the classic luminance
contrast between vehicle and bright road
surface”
The fact that the three dimensional
component is important also means that
extra attention is needed to avoid light in
directions where it can disturbing. The
direction of view of a car driver is usually
downwards but a pedestrian also looks
above the horizon in order to orientate
himself. It is therefore not surprising that
different glare systems exist for car drivers
(TI) and for pedestrians (I.A 0,5 ). With the
introduction of new compact light sources
for road lighting including LEDs, it is
important to note that during the
development of both glare concepts,
compact light sources for road lighting did
not yet exist. Improved glare restriction
concepts for both car drivers and
pedestrians, preferably based on a same
basic concept, are needed now.
Light that directly or indirectly brightens
the sky and/or buildings can rightly be called
light pollution. International guidelines for
limiting light pollution do exist and should
be followed. Restriction of light pollution
may automatically improve the overall
efficiency of a lighting installation because
light spillage outside the area to be lit is
avoided. The restriction of obtrusive light or
light pollution in fact is very much a
sustainability issue.
When lighting
The circumstances that determine whether
or not lighting is needed change
continuously during the dark hours. Road
Ingineria Iluminatului 2009; 11, 1: 5-12 9