Standards and Recommendations - Road Lighting: Fundamentals, Technology and Application - page 299

21.3.6 Restriction of Flicker

The restriction of disturbing flicker is specified exactly the same as in CIE: the
frequency range between 4 and 11 Hz should be avoided when the duration is greater
than 20 s. As has been stated already when discussing the CIE recommendation,
comparing this requirement with Fig. 20.19 of Chap. 20, shows that this requirement
does not seem to be strict enough.

21.3.7 Switching Steps

The adjustment of the lighting levels in the tunnel to changing outdoor lighting
situations can be done by means of continuous dimming or by switching in steps.
The American Standard does not give a quantitative limitation for the difference in
consecutive steps but a qualitative one in terms of, “the step difference should be
moderated in level and time”.

21.3.8 Night-Time Lighting

In tunnels with one-way traffic per tube the night-time average luminance should be
at least 2.5 cd/m 2 . In tunnels with two-way traffic per tube the average luminance in
the tunnel during the night time should be equal to the levels specified for the interior
zone for daytime use.

21.3.9 Short Tunnels

Exactly what geometric, surrounding, and traffic factors constitute a short tunnel
and what lighting is required for different short tunnels is taken from the 2004 CIE
Recommendation. Where CIE uses a decision-tree figure for this purpose (Fig. 21.2 ),
the American Standard has converted this figure into a table with the same values.

References

ANSI/IES (2011) RP22-11, Tunnel lighting
CEN (2003) Report CR 14380, Lighting applications-tunnel lighting
CIE (1990) Publication 88:1990, Guide for the lighting of road tunnels and underpasses
CIE (2004) Publication 88:2004, Guide for the lighting of road tunnels and underpasses