Luminance measurment
The requirements for tunnel lighting are determined by the nature of the human eye. The tunnel lighting must be controlled such that users, both during the day and by night, can approach, pass through and exit the tunnel without changing direction or speed with a degree of safety equal to that on the approach road. Especially by day the human eye needs to adapt to the lower lighting levels in a tunnel. The threshold lighting needs to be controlled such that drivers can perceive obstacles in the tunnel early enough to stop the vehicle.
The requirements for tunnel lighting are determined by the nature of the human eye. How well the eye recognises vehicles and other obstacles in a tunnel depends on the lighting and visibility as well as the reflexion characteristics of the road surface and the tunnel walls. Luminance is the measure representing what a human being perceives as brightness and as such is the main control variable for the tunnel lighting.
Tunnel lighting needs to be adapted to these environmental conditions, following these national and international guidelines:
- CIE 88:2004 Guide for the lighting of road tunnels and underpasses
- CEN Report CR 14380 Lighting applications – Tunnel lighting
- DIN 67524 Beleuchtung von Straßentunneln und Unterführungen (DE)
- RVS 09.02.41 Tunnelausrüstung Lichttechnik Beleuchtung (AT)
If measurement of luminance is designated, luminance meters are deployed in front of the tunnel portal and inside the tunnel if necessary.
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t/LUM-A Luminance meter
- Zoom lens to adjust the focus areas
- Sensor with V(λ) filter and silicon photo element
- Temperature compensated and long term stable amplifier for the photoelectric current using live zero
- Heated housing IP 67 made from stainless steel 1.4404
- Electronically controlled heating and temperature monitoring
- Mounting flange to adjust horizontal and vertical angle
- Fault indication by relay isolated (NC)
- Optional second outut channel for increased resolution at low lighting levels
- Surge protection
Luminance meter mounting positions
Luminance meter L20
Mount luminance meter to the tunnel portal according stopping distance. Luminance meter captures mean luminance with a field angle of 20° (drivers perspective). If the luminance meter cannot be mounted in stopping distance field angle need to be adjusted by zoom lense.
Luminance meter Lfe
Luminance meter has to be mounted on the tunnel wall and aligned to driving lane. Luminance meter captures luminance Lfe in the first part of access zone.
Luminance meter Lfi
Luminance meter has to be mounted on the tunnel wall and aligned to driving lane. Luminance meter captures luminance Lfi in interior zone.
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