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Methodology for Evaluation of Lighting Standards at an Expressway Tunnel Threshold Zone

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.