Civil Engineering Reference
In-Depth Information
Table 9.1
CIE lighting
classes for motorized traffic
and corresponding
(maintained) values of the
various lighting criteria
(CIE
2010
)
L
av
(cd/m
2
)
U
o
U
l
TI (%)
SR
M1
2.0
0.40
0.70
10
0.5
M3
1.0
0.40
0.60
15
0.5
M6
0.30
0.35
0.40
20
0.5
9.1.1
Lighting of Motorized-Traffic Routes
The basis of the recommendation is formed by six lighting classes: M1 to M6 (“M”
stands for motorized traffic). For each lighting class, values for the criteria: lighting
level, L
av
uniformity, Ul,
o
and U
l
, glare restriction, TI, and surround ratio, SR, are
specified. Table
9.1
gives the specified values for the highest, an intermediate and
the lowest class, M1, M3 and M6 respectively. As can be seen from the Table, the
lower the class number the higher the lighting quality required. The lighting levels
range from 2.0 to 0.3 cd/m
2
from class M1 to M6.
Which lighting class is applicable in a certain situation is dependent on the
following factors:
•
difficulty of the geometry of the road in terms of separation of carriageways and
of intersection density,
•
traffic characteristics in terms of speed, traffic volume, traffic composition,
possibility of parked vehicles,
•
average brightness of the area (ambient luminance),
•
quality of visual guidance and traffic-control signaling.
To determine the lighting class applicable according to these factors, CIE gives
different weighting values, V
w
, for all of these factors. Table
9.2
shows some of these
values. The sum of all weighting values, V
ws
, determines the number of lighting class
M according to:
M
=
6
−
V
ws
Example
Consider, for example, a main road with high-speed traffic (V
w
=
0.5) and
a high traffic volume (V
w
=
0.5) of mixed traffic only (V
w
=
1) with non-separated
carriageways (V
w
=
1) and a high intersection density (V
w
=
1), no parked vehicles
on the road allowed (V
w
=
0), a dark environment, viz. low ambient luminance (V
w
=
−
1) and good visual guidance/traffic control (V
w
=
0). The sum of all weighting
values, V
ws
, is: 0.5
+
0.5
+
1
+
1
+
1
+
0
−
1
+
0
=
3.0. The lighting class for this
example is therefore M
M3. Table
9.1
specifies the required lighting values
for this class. For example, the lighting level has to be 1 cd/m
2
. If, again as an example,
only motorized traffic instead of mixed traffic were to be permitted on this main road,
the weighting value for traffic composition would be 0 instead of 1. Consequently,
the resulting class would be M4 instead of M3, with a required lighting level of 0.75
instead of 1 cd/m
2
. This, indeed, is in accordance with the less difficult visual task
of the new situation.
=
6
−
3
=
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