https://www.osha.gov/SLTC/etools/logging/logsafe.html
Each employee in the immediate work area in the forest shall work in a position or location that is within visual or audible contact with another employee. Motor noise is not an acceptable signal.
Employees shall be spaced and duties organized such that the activity of one employee will not create hazards for other personnel.
Work areas shall be assigned so that a tree cannot fall into an adjacent occupied work area. The distance between adjacent occupied work areas shall be at least two (2) tree lengths of the trees being felled. The distance between adjacent occupied work areas shall reflect the degree of slope, the density of the growth, the height of the soil structure, and other hazards reasonably anticipated at that work site. A distance of greater than two tree lengths shall be maintained between adjacent occupied work areas on any slope where rolling or sliding of trees or logs is reasonably foreseeable.
While manual felling is in progress, no yarding machine shall be operated within two tree lengths of trees being manually felled.
