Civil Engineering Reference
In-Depth Information
luminances in a tunnel entrance. The lighting in a tunnel must therefore be such that
this adaptation problem is minimized, so that good visual performance is ensured
during the whole distance from the brightness outside the tunnel entrance, through
the darker tunnel interior, and on to the brightness outside the tunnel exit.
But even with good visual performance ensured, driving through a tunnel is con-
sidered by many motorists to be more demanding than driving along an open road.
Some drivers feel insecure and uncertain and a few are downright anxious. Even with
visual performance aspects satisfied, the tunnel entrance may still appear somewhat
as a black hole; and there is less room to manoeuvre in the tunnel itself. This lack
of confidence of the motorist approaching and driving through the tunnel may lead
to a hesitant driving behaviour, including reducing speed and change of lateral posi-
tion away from the tunnel walls (Martens and Kaptein
1998
). Needless to say, such
driving behaviour has a negative influence on traffic safety. Good tunnel lighting
can help the motorist to maintain a high sense of confidence when approaching the
tunnel entrance and driving into the tunnel.
In very long tunnels (to date, the longest road tunnel in the world is more than
24 km) the monotony that builds up during the drive through the tunnel may result
in sleepiness and in distraction of the driver away from the carriageway. A tunnel
simulation study has shown that lighting with some artistic elements in its design can
help break the monotony (Flø and Jenssen
2007
). It would be interesting to combine
such studies with the measurement of the brain activity of the test drivers along the
lines described in Sect. 3.10 of Part 1.
The basic purpose of tunnel lighting for motorised traffic can be summarised as:
•
to enhance the motorist's visual performance,
•
to maintain his sense of confidence.
Short tunnels and underpasses may also be used by slow-moving traffic, cyclists and
pedestrians. Where cyclists and pedestrians are concerned, the lighting should help
to promote not only visual performance and sense of confidence but also personal
security whilst also discouraging violence and vandalism. As far as personal security
is concerned, it is both:
•
a feeling of security
•
and actual security
that is important. As mentioned already in Chap. 1 of this topic, perceived insecurity
limits the mobility of especially young women and the elderly. A feeling of insecurity
especially arises when an easy escape possibility is not there, or seems not to be there.
Good lighting should thus already make the exit and the stretch beyond it clearly
visible at the moment of someone entering the tunnel.
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