Visual Performance for Motorists - Road Lighting: Fundamentals, Technology and Application - page 40

Fig. 3.28 Ranges of
reflectance factors that are
invisible (big crosses) 100 m
in front of a car with and
without headlights, together
with their percentage of
occurrence based on
pedestrian cloth-reflectance
factors. Fixed road lighting:
L av =

road lighting only

occur 2 %

1 cd/m 2 ; headlights:
E vert at 100 m

10 lx. Basis:
objects subtended an angle of
4 min

=

road lighting + headlights occur 18 %

2 5 20 50

1 10 100

Object reflectance (%)

an unlighted road, while driving in a car with low-beam high-intensity discharge-
lamp headlights, the detection distance of pedestrians decreases to almost half in a
situation with one oncoming car with the same type of headlights, compared to the
situation where there is no oncoming car (Saraiji et al. 2013 ). Bullough and Derlosfk
( 2004 ) showed that glare from an oncoming car increases the percentage of missed
targets on the road as well as increasing the reaction time to targets that are not
missed. Dangerous last-minute evasive manoeuvres may be the result. Fixed road
lighting minimises the problem because it raises the adaptation level of the drivers.
To illustrate how important this positive effect on visibility is, we show the results
of a French test covering three different situations (Bacelar 2004 ): one with dipped-
beam lights only, one with dipped-beam lights and an oncoming car with dipped
beam, and finally a situation where fixed road lighting of good quality is added in
conjunction with dipped beams (Fig. 3.29 ). From this figure it can be seen that the
visibility level in the situation of a car with his dipped beam on (top bar of the figure)
decreases considerably when there is an oncoming car (middle bar). The same situa-
tion of an oncoming car, but now with road lighting (lower bar) doubles the visibility
level.

3.8 Pedestrian Road Crossings

With good road lighting pedestrians on road crossings are visible from a relatively
large distance in negative contrast. Closer to the crossing the pedestrians become
visible in positive contrast. This is because of the vertical illumination of a car's
headlamps. The purpose of additional lighting at a road crossing is specifically to
draw the attention of motorists to the presence of the crossing. The presence of
extra lighting columns at the crossing may, even during the daytime, in itself help
to signal the presence of the crossing. A higher lighting level at the crossing than on