Do not perform overhead work under any circumstances in places where people or vehicles are present or where they may enter during the course of the work. This is to prevent the possibility of an object falling and hitting a person or vehicle.
Barricade and mark areas affected by overhead work to keep people and vehicles out of the area and warn them of the hazard. Do not leave tools, materials, and equipment unattended on ladders, scaffolds, or platforms when there is a chance that the items may fall or be dislodged.
29 CFR 1926, Subpart G, Subpart L.