Warning lines serve as fall protection only on roofs no steeper than two in twelve, and roofers working between the roof edge and the warning line get personal fall arrest, personal fall restraint, a guardrail, a safety net or a safety monitoring system; the warning line itself is erected around all sides of the work area at the distances from the edge the federal criteria require (six feet, or ten feet perpendicular to mechanical equipment travel), with flagged, stanchion-supported lines of the specified height and strength and barricaded access paths.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.