Tunnel Lighting

L20 threshold luminance in road tunnels: CIE 88:2004 calculation with worked examples

Threshold luminance Lth is the parameter that sizes any tunnel lighting installation. Here is how to compute L20 step by step per CIE 88:2004 and UNI 11095, with three worked examples and a design checklist.

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Galleria stradale con illuminazione LED della carreggiata. Immagine illustrativa generata con AI.

Summary

Threshold luminance Lth is the parameter that sizes any tunnel lighting installation. Here is how to compute L20 step by step per CIE 88:2004 and UNI 11095, with three worked examples and a design checklist.

Topics

  • L20 threshold luminance tunnel
  • CIE 88 Lth calculation
  • UNI 11095 tunnel lighting design
  • tunnel access zone lighting
  • road tunnel threshold zone
  • CIE 88 k factor

Category

Article from the Tunnel Lighting section. Reading time 10 min. Updated on 2026-07-20.