Abstract: The luminance L₂₀(S) varies considerably from time to time throughout the day and obtaining its value in real-time during urban tunnel operations is challenging. Thus, the authors propose a real-time calculation method that takes solar illuminance as the input variable and couples the sky and ground scene luminance into L₂₀(S) in combination with a three-dimensional (3D) printed tunnel scaled model. The Luhua road tunnel in Beijing is taken as the measurement object. A 3D printed tunnel scaled model is used instead of an actual tunnel to explore the change rule of ground scene luminance, and a quantitative regression model of ground scene luminance and solar illuminance is established. The calculated values from the International Commission on Illumination(CIE) and Perez models are compared with the measured values  based on solar illuminance in the present study. The CIE model with a smaller error and easier calculation is determined as the sky luminance. The error rates are 4.26% and 6.11% under sunny and cloudy conditions, respectively. The average error rate of the calculated values of the coupled L₂₀(S) calculation model and the measured values in different seasons and weather conditions is below 10%, demonstrating the accuracy and applicability of the realtime calculation method for tunnel access zone luminance in all seasons and weather conditions.

Key words: tunnel access zone luminance, three-dimensional printed tunnel scaled model, solar illuminance, tunnel lighting