Road tunnel lighting is an important subject and design of the lighting is done based on certain parameters like, max speed allowed, stopping distance, volume of the tunnel, external luminance and topography of the tunnel etc ..
Standards followed while designing is based on CIE 88:2004,ANSI/IES RP22-11, and in India it is widely followed with the general guidelines of IRC SP 91:2010 , IRC SP87:2013.
Tunnel lighting is divided in to zones and luminance levels are controlled automatically to adopt the safer movement inside the tunnels. The poorly designed tunnel lighting may lead to accidents as the human eye cannot cope with the rapid change in brightness when entering inside the tunnel.
The resulting black hole syndrome can render the driver effectively blind for a small period.
The illuminance measurement is used by the lighting control system to verify the actual lighting intensity applied to the tunnel.