Traffic light signals let both the driver outside and the loading crew inside know whether the loading bay is ready for the truck to dock and/or loading can commence.
Most traffic light systems in use have two signal generators (red and green). Red and green signals can also be combined in one generator.
Two generator models are in widespread use: those fitted with standard light bulbs, and those with much better quality LED lamps. Although slightly more expensive to buy, LED lamps are much cheaper over the life cycle as they last much longer than conventional light bulbs. Added to which, LED lamps are much brighter, making the respective colour easy to recognize, even in sunlight. The functions of the light systems are agreed individually with users.