Travel restraint, warning lines and control zones

When guardrails are not practicable, the next best option is usually to stop workers from reaching the edge at all. Travel restraint does this with personal equipment: a harness or belt, a lanyard or lifeline, and an anchor placed so that the worker runs out of line before reaching the hazard. Marked warning lines, control zones and safety monitors try to do the same thing with markings and supervision. This lesson explains how each method works, how to set it up correctly and where its limits lie.

How travel restraint works

A travel restraint system is a tether. The worker wears a full body harness or, where the rules allow, a safety belt, connected by a lanyard or a rope lifeline to an anchor. The total length from the anchor to the worker's attachment point is set so that the worker can reach the work but not the edge. If the system is set up correctly, the worker can lean against the tether at the end of its reach without being able to fall over the edge, so no fall ever starts.

Because no fall occurs, a travel restraint system does not need the energy absorbers, clearance distances or rescue arrangements that fall arrest needs, and its anchors can be lighter. That makes restraint attractive on flat roofs, around floor openings and near loading edges. But the advantage disappears if the system is set up so that the worker can reach the edge. Then it becomes an improvised fall arrest system, with an anchor, lanyard and harness that may not be designed for the forces of a fall.

Setting the length

The key calculation for travel restraint is the maximum length of the tether. Measure the shortest distance from the anchor to the edge, in any direction the worker could move, and subtract a margin so that the worker's body cannot reach or lean over the edge.

Here \( L_{\text{max}} \) is the total length from the anchor point to the harness attachment, including connectors, anchorage straps and any slack, \( D_{\text{edge}} \) is the shortest horizontal distance from the anchor to the edge, and \( m \) is a safety margin that accounts for the worker's reach, body position and stretch of the equipment. Many employers use a margin of at least the worker's arm-and-body reach beyond the harness attachment.

Corners and irregular roofs matter. An anchor placed in the middle of a long, narrow roof may allow a worker to reach the near edge if they walk sideways. Draw the reach circle on a roof plan, as in the figure, and check that it stays inside the edge everywhere the worker can go. Where one anchor cannot cover the work area safely, use several anchors, a horizontal lifeline set back from the edge, or a rail system with a trolley that keeps the worker inside a safe band.

Adjustable lanyards and rope grabs

Many restraint systems use an adjustable rope lanyard or a rope lifeline with a rope grab, so that the worker can shorten the tether near an edge and lengthen it in the middle of the roof. This flexibility is useful but creates a risk: a worker who lets out too much rope can reach the edge. Train workers to adjust the length as they move, mark maximum lengths on the rope, or use fixed-length lanyards where possible. Self-retracting devices are sometimes used for restraint, but they extend as the worker walks away, so they do not restrain unless they are fitted with a length limiter or the anchor is placed so that their full length cannot reach the edge.

Anchors for restraint

Because a restraint system should never arrest a fall, its anchors can be lighter than fall arrest anchors, but only if the system truly prevents a fall. OSHA's 1910.140 requires travel restraint systems to keep the worker from reaching the fall hazard, and ANSI/ASSP Z359 guidance commonly calls for restraint anchorages of at least 1,000 lb, or twice the foreseeable force, compared with 5,000 lb for fall arrest. Anchors intended only for restraint should be clearly marked as such. Never use a restraint anchor for fall arrest.

Fall restriction and positioning

Two related systems allow a small amount of movement or fall:

• work positioning systems hold a worker in place while leaving the hands free, for example a pole strap for a line worker or a positioning lanyard for a rebar worker on a wall. They are not designed to arrest a fall from an edge and are usually combined with a separate fall arrest system;
• ladder safety systems on fixed ladders, and positioning systems, limit free fall to a short distance. OSHA limits free fall on positioning systems to 2 ft and on ladder safety systems to 2 ft.

Marked lines and control zones

A warning line or control line is a rope, wire or chain, flagged so that it is easy to see, set up at a distance from an unprotected edge. Workers outside the line, away from the edge, may work without personal fall protection under specific conditions. Anyone who crosses the line, into the zone next to the edge, must use guardrails, restraint or fall arrest. The idea is to keep most of the work and the traffic well back from the edge.

OSHA permits warning line systems in specific situations. In construction, 1926.502(f) requires warning lines on low-slope roofs to be at least 6 ft from the roof edge, and at least 10 ft from the edge parallel to the direction of mechanical equipment operation. Lines must be flagged at least every 6 ft, be 34 to 39 in above the roof, and resist a tipping force of at least 16 lb. During roofing work on low-slope roofs, warning lines must be combined with guardrails, safety nets, personal fall arrest or a safety monitoring system for work between the line and the edge. In general industry, 1910.28(b)(13) allows designated areas on low-slope roofs: work less than 6 ft from the edge needs guardrails, nets, restraint or arrest; work 6 to 15 ft from the edge may use a designated area; and infrequent, temporary work 15 ft or more from the edge may rely on a work rule that keeps workers out of the 15 ft zone.

Safety monitors and controlled access zones

A safety monitoring system uses a competent person to watch workers near an edge and warn them. OSHA permits safety monitoring alone only for roofing work on low-slope roofs 50 ft wide or less, and otherwise in combination with warning lines. The monitor must be on the same surface, within sight and voice range of the workers, with no other duties that distract them. Controlled access zones, under 1926.502(g), mark off an area where leading edge, precast concrete or residential work is done without conventional fall protection under a written fall protection plan prepared by a qualified person under 1926.502(k). The plan must explain why conventional protection is infeasible or creates a greater hazard, and only workers named in the plan may enter the zone.

Why these are the weakest options

Marked lines, control zones and monitors do not physically stop a fall. They depend on workers noticing the line, respecting it and not stepping over it while carrying materials, walking backward or working in poor light. They work best where the work is far from the edge, the line is highly visible, and anyone crossing it must use real protection. They work poorly where workers frequently need to go near the edge, where materials must be moved to and from the edge, or where the roof is crowded. In those situations, guardrails or restraint are almost always the better choice.

Restraint on slopes and around openings

Travel restraint works best on flat or low-slope surfaces, where a worker who leans against the tether can stand steadily. On steeper roofs, a worker may slide down the roof surface until the tether comes taut, and if the tether is long enough to reach the edge, the system becomes fall arrest by default. On steep roofs, use anchors placed so that the tether stops the worker well up the slope, combined with fall arrest equipment rated for the anchor position, or use scaffolds and guardrails at the eaves.

Restraint is also useful around floor openings, roof hatches and open loading edges, where a worker must work near a hole for a short time. Place the anchor so that the reach circle stops short of the opening on every side, and remember that the worker may need to step around the opening to reach the far side. Two anchors on opposite sides, or a short rail with a trolley, may be needed.

Common set-up errors

Investigations of falls involving restraint systems point to a few recurring errors: an anchor placed for one task and used for another without rechecking the reach; an adjustable lanyard let out to reach a tool and never shortened; a lanyard connected to a side D-ring rather than the attachment point the manufacturer specifies; two lanyards clipped end to end to reach farther; and a self-retracting device used as if it were a fixed tether. A simple check before each task, measuring or pacing the reach to the nearest edge, prevents most of them.