TRILUX Luminaires - Proljus AB

Photometrics
Road lighting
Lighting quality characteristics
The procedure for determining the quality
characteristics of a lighting system for a
specific road comprises three steps:
The procedure for determining the road
lighting quality characteristics according to
CEN/TR 13201-1 and EN 13201-2 is explained
with the aid of the following example:
Example: Major traffic road
A major traffic road within a small town has
to be illuminated. No road users are to be
excluded: Cyclists are common and pedestrians
usually cross the road at crossings that
do not have traffic lights. Which photometric
data have to be satisfied by the lighting
installation?
The lighting class to be used shall be selected
according to the diverse tables for the
lighting situations A1 to E2 that are contained
in the Appendix A to CEN/TR 13201-1.
For the selected example involving a major
traffic road, that is the table for the B2 lighting
situation.
Taking the max. speed of 60 km/h and the
main road users (motor vehicles, including
slow moving vehicles) as well as cyclists and
pedestrians into consideration during step 1
results in the lighting situation B2, which belongs
to the lighting classes ME2 to ME6 with
the luminance evaluation. Based on a traffic
analysis, the mean daily traffic (MDT), which
is the total traffic volume occurring within a
number of days divided by the number of
days, has been determined at more than
7000 vehicles/day. The road was evaluated in
a dry state, there are no measures for slowing
traffic, the number of junctions per km
is < 3 and the difficulty of the driving task is
normal.
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Step 1
Selection of the
lighting situation
according to CEN/TR 13201-1
Step 2
Selection of the
lighting class
according to CEN/TR 13201-1
This results in the lighting class ME4b twice
and the lighting class ME3c once. The final
lighting class has to be selected now from
the lighting classes in the example ME4b,
ME4b and ME3c based on other criteria. This
can be implemented using another table that
supplements the selection criteria of the
table for the B2 lighting situation with regard
to other selection criteria. These criteria are:
• Conflict zones, i.e. areas where motorised
traffic streams cross each other, e.g. at
crossings without traffic lights, at roundabouts
or in areas prone to traffic jams
in front of traffic lights or in areas where
there are other users, e.g. in shopping
streets.
• Complexity of the visual field, i.e. visual
influences within the field of vision, which
can be misleading, distracting, disturbing
or annoying, e.g. with extreme advertising
structures.
Consequences for the major traffic road:
Conflict zones are not present, the complexity
of the visual field is normal (there are no
extreme annoyances, e.g. due to advertising
structures), parking along the side of the
road is permitted, the ambient luminance is
average and the traffic flow of cyclists is
high. Consequently, the planning should be
based on the lighting class ME3c.
This results in the following photometric
system data:
• Maintenance value of the mean luminance
L – = 1.0 cd/m²
m
• Total uniformity Uo = 0.4
• Longitudinal uniformity Ul = 0.5
• Threshold increment TI = 15 %
• Ambient illuminance relation SR = 0.5
Step 3
Determination of the lighting
quality characteristics
according to EN 13201-2
L – m Is the mean luminance as maintenance
value, which may not be undershot at
any time.
U o Total uniformity, relation of the lowest
luminance (or illuminance) to the mean
value on the road surface.
U l Longitudinal uniformity, relation of the
lowest to the highest luminance on the
middle of the traffic lane.
TI Threshold increment, measure for the
loss of visibility of an object as a result of
physiological glare due to extremely
bright luminaires.
SR Ambient illuminance relation for improving
spatial orientation such that the
areas next to the road can also be perceived,
even if they are not illuminated
themselves. SR is the relation of the
mean illuminance of both surrounding
surfaces outside the road to the mean
illuminance of the outer traffic lane of
the road, with both surfaces having the
same width.