What is the issue?
WorkSafe’s High Hazards Unit has recently been notified of rollover incidents involving the use of
trucks in open cast mines, alluvial mines and quarries. The trucks involved range from road certified truck
and trailer units through to heavy off-road articulated dump trucks. These incidents resulted in workers
being injured and in one recent case, a tragic loss of life. Any truck rollover has the potential to cause harm
to the truck operator, passengers and/or bystanders. This safety alert highlights the serious health and safety risks for operating articulated machinery in open cast mines, alluvial mines and quarries.
How did these incidents happen?
Key factors that were found included:
– uneven ground, particularly when tipping
and reversing
– excessive speed
– loss of ground stability or subsidence beneath
the truck
– hold up of material in the tray when tipping
– use of machinery outside of design capability
– under inflation or rapid deflation of tyres
– roads being too wet causing loss of traction
– tipping at a 90 degree angle to the dump tray
– untrained or inattentive drivers.
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Vehicle incident one
A truck was tipping material and backed up onto a load that was dumped previously. The material was sticky and hung up in the tray causing the trailer to tip over.
Vehicle incident two
Large rocks were caught up within the tailgate of an articulated dump truck (ADT) tipping down
grade without a dump windrow. This caused the ADT to lift upwards allowing the cab to lift off the
ground and rotate
Vehicle incident three
A service truck at an open cut mining operation drifted sideways when negotiating a sweeping right hand bend. The truck travelled approximately 20 metres before it lost traction at its rear wheels which spun the truck around 180 degrees. The left wheel then gripped into the road surface tipping the truck onto its side.
Use of heavy machinery in mines and quarries is critical risk that the sector needs to address through
effective controls and effectiveness monitoring. Critical risks controls must be understood by all
personnel and applied without exception to ensure everybody’s safety.
What can be learned?
It is essential to have and to implement a vehicle maintenance plan, road way design, tip design as
well as a traffic management plan. These plans should address relevant controls to prevent rollovers.
These controls may include:
– maintaining truck suspension systems and check
to ensure they are in good order appropriate for
the environment
– ensuring tipping areas are level, without cross grade
– tipping is not carried out in manoeuvring zone
of any other vehicles and machinery
– keeping tipping areas stable, capable of withstanding
truck wheel pressures, and not prone to subsidence
– ensuring tyres are in good condition and at
correct pressure
– fitting speed limiting controls to vehicles
– having safety functions in place to alert the
operator of a pending overturning of the dump
body or out-of-balance situation
– checking for material that has hung up in the
tray while tipping and knowing material density
and flowability
– operating trucks within original equipment
manufacturer (OEM) design limits
– operator training, induction and observation
– maintaining haul roads to design standards,
without pot holes and loose rocks
– ensuring road watering procedures do not make
roads slippery
– ensuring out-of-control vehicle emergency recovery
procedures are adequate
– operating brakes and retard systems to OEM standards
– undertake regular static and dynamic brake testing
programmes to ensure optimal braking efficiency
– disabling machinery while turbo timers are
in operation.
Controls to mitigate the risk of injury following a truck rollover should also be implemented and include:
– the fit-out and use of operator seat restraints
– the use of operator protective structures
– measures to ensure all tipping can only be completed in line so truck is not at an angle to the dump tray
and in the fall zone
– appropriately designed and maintained windrows,
berms and bunding.
More information
worksafe.govt.nz/topic-and-industry/extractives/
guidance-position-statements/health-and-safety-atopencast-mines-alluvial-mines-and-quarries/
www.nzta.govt.nz/assets/resources/roadcode/truckloading-code/docs/tlc.pdf
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