They called them chicken lights cause back then hauling frozen chicken paid the most money so they could afford extra marker lights and chrome accessories. Chicken money =more chicken lights.
It's a derogatory slur. A "chicken hauler" is the lowest level in the cast of southern truck drivers, hauling live poultry in open cages to market. A lowly chicken hauler truck may often be decorated with "chicken lights" in order to bring his status up in the world via ornamentation.
Chicken lights are put on the front of truck bumper to help the driver get as close as possible to an object before having to make a corrective turn or maneuver. The reason there called chicken lights is because truckers were/are afraid of damaging the nose of their rigs.
None of these are correct.