A fall is not decided by the height. It is decided by the last few inches. Gravity sets the speed a body carries into the ground; the ground decides how fast that speed is taken away. A harness is a device for changing that one number.
Start with the speed. A body that falls six feet reaches the ground at about thirteen miles an hour; from twenty feet, roughly twenty-five; from thirty, about thirty. Those are ordinary free-fall numbers, and by themselves they are not the injury. Thirteen miles an hour is the speed of a fast runner. The injury is in the stop.
Here is the whole of it in one line of physics. The average deceleration of the stop, counted in g’s, is the height of the fall divided by the distance the body travels while it stops. Fall six feet and stop in two inches, about what flesh gives against concrete, and the average is some thirty-six g, thirty-six times the pull of gravity, with peaks higher still. Stop the same fall over three and a half feet and the average drops below two.
The rule. That is the physics the federal fall rule is written in. On a construction site, a worker on a surface with an unprotected side or edge six feet or more above a lower level “shall be protected from falling” by guardrails, safety nets, or a personal fall arrest system (29 CFR 1926.501(b)(1)). The rule for the harness reads like an engineering drawing of the same equation. The system must keep a worker from free falling more than six feet or striking any lower level, must limit the arresting force on a worker in a body harness to 1,800 pounds, and must bring the worker to a complete stop within a deceleration distance of three and a half feet (29 CFR 1926.502(d)(16)).
Read those numbers together and the design explains itself. The harness does not make the fall shorter. It makes the stop longer. The lanyard and the webbing are built to give, so the same energy is spent over feet instead of inches, and the force limit keeps the peak inside what a body can survive.
The body. Without the harness, the ground does the stopping, and it does it through the body’s own structure. Feet first, the heel bone takes the load. Calcaneus fractures most often come from high-energy events that load the bone along its length, and falls from height are one of the two leading causes; physicians are taught to examine the entire spine whenever the heel breaks in a fall, and more than seven in ten people with a calcaneus fracture turn out to have other injuries too (StatPearls). Head first or side first, the same arithmetic lands on the skull, the chest, or the pelvis, which is the pattern Over the Top follows off a freeway wall.
The count is steady. In 2024, falls, slips, and trips killed 844 workers in the United States, and 370 of them worked in construction and extraction jobs (Bureau of Labor Statistics).
It is the same principle, at human scale, that runs through the crash pages here. The Fixed Object is a car that finds something that will not give, and Delta-V is the speed given up in the stop. A harness is the rare safety device that works the way a crush zone does: it buys distance, and distance is survival.
Whose job it is. The rule is written for the employer: it is the employer who must see that the worker at six feet is protected. When the protection that was required is missing and a worker falls, that failure is central to the case, and the next question is who else was on the site: the general contractor who controlled it, the company that supplied the anchor or the lanyard. A Texas employer that carries workers’ compensation answers through that system; one that does not can be sued directly and loses its old defenses. The paths are laid out on the falls and crush injuries page, in third-party claims, and on the nonsubscriber page.
Gravity is not negotiable. The stopping distance is. Six feet is where the law stops negotiating.
The fall rule: 29 CFR 1926.501(b)(1). The harness: 29 CFR 1926.502(d)(16). The heel: Davis, Seaman, and Newton, Calcaneus Fractures (StatPearls, National Library of Medicine, updated July 2023). The count: Bureau of Labor Statistics, National Census of Fatal Occupational Injuries in 2024. Fall speeds are ordinary free-fall figures, rounded; the stopping arithmetic is the work-energy relation, averaged over the stop. This is general information, not medical or legal advice.
