Visual Performance and Sense of Confidence - Road Lighting: Fundamentals, Technology and Application - page 290

20.10.2 Underpasses for Pedestrians and Cyclists Only

Given the relatively-slow speed of pedestrians and cyclists, the delay in adaptation
when entering a relatively dark underpass during the hours of daylight is not usually
a problem as far as their ability to see possible obstacles is concerned. The lighting
levels needed here during the hours of darkness will thus suffice for the daytime situ-
ation. However, the security aspect should receive extra attention. Many pedestrians
and cyclists feel scared in underpasses and are indeed vulnerable to threats or attacks.
An underpass with bright walls and bright exit areas will enable these users to be
visually aware of their surroundings, so contributing to a feeling of security. At the
same time, this will discourage those with hostile intentions, because they will know
that they are easily visible. The apparent brightnesses in an underpass are negatively
influenced by the delay in adaptation of the pedestrian or cyclist passing through it.
Practical experience has shown that luminances of some 20 cd/m 2 are the minimum
needed to create the apparent brightness required. This means that for walls of high
reflectance (larger than some 0.60) and for exit areas, an illuminance of some 100 lx
is called for. Especially important are those sections of the walls that coincide with
the end of the normal viewing lines of pedestrians and cyclists on their way through
the tunnel or underpass.

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