Health, Safety and Welfare on Site
The machine is the hazard
Nearly every question in this domain comes back to one idea: the mini digger is the hazard and everyone else on site is exposed to it. You must be able to describe the slew radius (the full circle swept by the house, counterweight, boom and bucket), the tail swing of the counterweight, and the blind spots - particularly down the right-hand side and directly behind the cab. Mirrors, cameras and a reversing alarm help, but they never replace a trained signaller using recognised hand signals or radio.
Segregation and exclusion zones
Site traffic management should separate plant from pedestrians using physical barriers and marked walkways. Plant and people never share a route without a control. When digging, define an exclusion zone, mark it, and keep everyone out - including the supervisor who "just wants a quick look".
Ground, services and edges
Assume services are present. Use service drawings, a cable avoidance tool and safe digging (hand-dug trial holes) near marks. Treat overhead lines as live and use goal posts or a diversion. Keep spoil, materials and plant back from excavation edges, barrier the edges, and provide ladder access.
Health and welfare
Control noise, dust (water suppression, suitable masks), diesel fumes (never run plant in enclosed spaces) and hand-arm vibration from long periods on a breaker. Welfare - toilets, washing water, drinking water and a rest shelter - is a legal requirement, not a courtesy.
Worked rule of thumb
Set the exclusion radius at the machine's maximum reach plus at least 1 m, and keep spoil at least 1 m back from any trench edge.
Traps
Carrying passengers or riding in the bucket; standing in a trench while a machine works alongside; assuming the reversing alarm clears the area; refuelling with the engine running.