Subcontractors’ ability to evaluate site conditions for unacceptable hazards varies with the type of hazardous condition. Subcontractors can be expected to observe the work and the jobsite at all times because it is their employees performing all of the actual construction work, and paragraph 1926.20 of the OSHA CFR requires ‘‘frequent and regular inspections of the sites, materials, and equipment to be made by competent persons designated by the employers.’’ Also, subcontractor foremen and other managers observe the work regularly to ensure that the work is accomplished within productivity and quality goals. Subcontractors therefore have a high ability to identify visible unsafe conditions such as broken ladders and slippery surfaces. On the other hand, subcontractors may have a low ability to identify hidden unsafe conditions, such as structurally deficient work platforms or hazardous electrical or atmospheric conditions, unless these conditions are routinely faced in their work.