The road tunnel structure is shown in Figure 1. Lighting requirements for specific areas of the road tunnel in an emergency are recommended as follows.
2.1 Lighting for drivers
2.1.1 lane
In the event of a failure of normal power supply, refer to CIE 88:2004[3] Chapter 8 to meet the appropriate lane lighting requirements.
2.1.2 Emergency parking belts
At all times, the average level of illumination provided by the emergency parking lighting must not be less than 3 times the illumination of the adjacent lane (using the same light source) or less than 2 times the illumination of the adjacent lane (using a different light source).
At all times, the total illuminance uniformity of the emergency stop zone shall not be lower than the total illuminance uniformity of the adjacent lanes. The color rendering index Ra≥60 for emergency parking lighting.
When calculating the main Tunnel lighting threshold increment (TI), all lighting fixtures in the field of view, including those with emergency parking, should be taken into account.