Prevent deadly accidents from poor communication between dock and
drivers
Clearly indicate status of trailer - red for loading/unloading,
green for okay to depart
When light is red for driver, light inside is green for dock
operations to take place (if dual lights are in use)
Driver instantly knows trailer status with a quick glance
Differences between models that begin in SG20 and SG10: SG20 models come with power switch and bulb flasher while the SG10 units only come with the light unit