Civil Engineering Reference
In-Depth Information
Fig. 7.5
Revealing power
(
RP
) of cloth targets at the
darkest location on the road
as a function of the average
road-surface luminance (
L
av
)
for
U
o
= 0.4 and
TI
=10%.
Visual angle 7
(20
100
U
o
= 0.4 TI = 10 % 7 min
RP
(%)
75
20 cm
at 100 m, the safe stopping
distance at a speed of
100-120 km/h). Age 30, 50
and 60 year
×
50
30 yrs
50 yrs
60 yrs
25
0
0.1
0.2
0.5
2
5
1
10
L
av
(cd/m
2
)
Fig. 7.6
Revealing power
(
RP
) of cloth targets at the
darkest location on the road
as a function of the average
road-surface luminance (
L
av
)
for
U
o
= 0.4 and
TI
=10%.
Visual angle 9
(20
100
U
o
= 0.4 TI = 10 % 9 min
RP
(%)
75
20 cm
at 75 m, the safe stopping
distance at a speed of
80-90 km/h). Age 30, 50 and
60 year
×
50
30 yrs
50 yrs
60 yrs
25
0
0.1
0.2
0.5
2
5
1
10
L
av
(cd/m
2
)
of the veiling luminance. Under the same lighting conditions, the veiling luminance
of a 50-year-old is a factor 1.3 times higher than that of a 23-year-old. For 60-year-old
the factor is 1.6 and for 70-year-old 2.2 (Fisher and Christie
1965
; CIE
2000
). So,
from all this, it is evident that it is important that special attention be paid to proper
glare restriction for the elderly.
A general remark has to be made: ageing effects of the visual system vary con-
siderably between individuals. For example, some people have to undergo a cataract
surgery in their early 50s, while some others do need it until much later, when they
sometimes are still even able to read without spectacles.
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