It　is　obvious　that　luminance　reduction　coefficient　standards　do　not　satisfy　a　driver＇s　comfort　and　safety　in　an　expressway　tunnel　threshold　zone.　In　fact,　the　standards　may　impair　a　driver＇s　vision　and　increase　the　probability　of　accidents.　Smaller　luminance　reduction　coefficients　are　economical　but　unsafe.　The　threshold　zone　lighting　of　existing　and　newly　designed　tunnels　needs　to　be　analyzed　to　prevent　safety　luminance　problems.　This　paper　provides　a　method,　CRP,　to　evaluate　drivers＇　safety　and　comfort　caused　by　tunnel　luminance　reduction　coefficients,　based　on　analyzing　drivers＇　visual　demands.　It　consists　of　field　experiments　to　examine　CRP　and　luminance　reduction　coefficient　under　different　operating　speeds　in　expressway　tunnel　threshold　zones.　A　regression　model　is　developed　according　to　the　comfort　and　safety　threshold;　this　was　based　on　changing　the　driver＇s　rate　of　pupil　adjustment　by　20%,　by　which　we　can　obtain　the　comfort　and　safety　luminance　reduction　coefficient.　The　expressway　tunnel　threshold　zone　luminance　reduction　coefficient　standard　of　0.031　was　determined　at　a　speed　of　60km/h.　This　is　higher　than　the　Chinese　standard.