some old tunnels with long years hps lighting service, but a rather dark brightness because of light Attenuation. lower buget owner can save big investment volume by choosing the 485 Solution.

there is also PLC -- power line communication single lamp Controller, but there is a shortadvange, once any of the lamp is failure, the maintanence meet a critical problem to repair it by shut off the whole group's power.

a better solution can be choosed is the loop Circult control Solution.

all of the above solutions have been widely using in our different 2000 tunnels in the past 8 years. tunnel length from 300m/500m ~ 2km/5km-14.3km.

p LC & LoRa hybrid solution on the highway road Lighting/Street lighting projects