SEA/General/TBT-SEA-005

Fog and Poor Visibility Working

Seasonal & Weather › General › Fog and Poor Visibility Working

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Fog, mist, heavy rain, and low cloud reduce visibility on construction sites, increasing the risk of collisions and falls.
Reduced visibility affects plant operators who cannot see pedestrians, banksmen who cannot see vehicles, and all site movements.
Crane operations must be assessed and potentially suspended when the operator cannot clearly see the load and landing area.
Vehicle speed must be reduced and additional lighting used when visibility drops below safe levels for the road speed.
Pedestrian routes must be adequately lit — workers walking in fog without reflective clothing are invisible to plant operators.
Working at height in fog reduces the ability to judge distances and see edge protection, increasing the risk of falls.
Banksmen and signallers must use illuminated wands and enhanced signals when hand signals are no longer clearly visible.
A stop-work trigger should be defined in the site procedures for visibility below which certain operations must cease.
Fog can occur suddenly, particularly on low-lying sites near rivers, canals, and bodies of water — monitoring is essential.
All workers must wear hi-vis clothing with reflective strips to maximise their visibility to others in poor conditions.

Invisible pedestrians	A worker without reflective clothing in fog is invisible to plant operators — struck-by incidents occur because people cannot be seen.
Crane visibility	A crane operator who cannot see the load or landing area loses control of the operation — lifts must stop in poor visibility.
Sudden onset	Fog forms rapidly on low-lying and waterside sites — conditions can change from clear to zero visibility within minutes.

Don't

Reduce vehicle and plant speed when visibility deteriorates below safe levels.
Increase lighting on access routes and work areas during fog and poor visibility.
Wear hi-vis clothing with reflective strips at all times in reduced visibility.
Assess crane operations and suspend them if the operator cannot see the load clearly.
Use illuminated wands and enhanced signals when hand signals are not clearly visible.
Define and follow the site stop-work visibility trigger for high-risk operations.
Monitor weather conditions for fog warnings, especially on low-lying or waterside sites.
Ensure banksmen maintain visual contact with both the plant and nearby pedestrians.
Increase communication between plant operators and ground workers using radios.
Brief the team on reduced visibility procedures at the start of any affected shift.

DON'T drive at normal speed when visibility is significantly reduced by fog or mist.
DON'T work in fog without adequate lighting on access routes and work areas.
DON'T move around site without hi-vis clothing and reflective strips in poor visibility.
DON'T continue crane operations if the operator cannot clearly see the load and landing.
DON'T rely on standard hand signals when they cannot be seen clearly at distance.
DON'T ignore the visibility stop-work trigger — some operations must cease in fog.
DON'T assume fog will lift quickly — it can persist for hours on low-lying sites.
DON'T allow banksmen to operate if they cannot maintain sight of plant and pedestrians.
DON'T rely on shouting for communication — use radios when visibility reduces sight lines.
DON'T start work without briefing the team on fog procedures and enhanced precautions.

See also: Winter Working Safety | Night Working Safety Awareness

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