The job of signalperson is an old and ancient custom. Before electronic communications, signalpeople used flags and lights for communication. Some still do depending on the circumstances. In fact, the military still uses lights and flags, especially in combat situations.
You’ve likely seen people on construction sites who stand around with flags and direct traffic. They don’t just direct cars and trucks on the road. They also direct heavy equipment such as cranes.
The signalperson must understand how every piece of equipment maneuvers and have a thorough understanding of their limitations. That includes how the boom swings, how buckets raise and lower, clearances, and a whole bunch of safety factors. These safety factors are the reason signalpeople must be OSHA certified.
Other things signalpeople must understand well are weather and terrain circumstances that can affect equipment maneuverability.
For instance, if it has rained within the last day or so, will the ground be too soft for tracked vehicles? What about wheeled vehicles? How will clay beneath the surface affect turning on the job site? Will vehicles move faster or slower as a result of weather and ground conditions?
These are all important considerations and the signalperson must be able to account for them as they direct heavy equipment on the work site. It is imperative for the safety of the entire work crew and any civilians in the area. That’s why it is important to get the best signalperson training you can get prior to taking a job in this specialty.