Using the six-wheel vehicles as water carts may present too great a risk as four of the six incidents, which all occurred in the last six months, were configured as water carts.

Although the rollovers are potentially dangerous, all operators involved in the reported incidents escaped unharmed.

Factors in an articulated truck rollover can include uneven ground conditions. Although the vehicle is designed for rough terrain, ground conditions worsen speed and can cause instability.

Many such trucks are fitted with a water cart body in place of the dump tray. Unstable loads cause vehicle instability and water is a most unstable load, even though the tank must contain baffles to reduce the effect of the water “sloshing”

If the articulated connection lacks the front to rear axle rigidity of a single chassis, this can also contribute to rollovers. A rigid chassis absorbs the “slosh” of the water in a tank, reducing the potential to roll.

In cross slope travel situations, the centre of gravity can move outside the body line of articulated trucks, which then become unstable on cornering.

An untrained or inattentive driver, excessive speed, and overloading together increase the possibility of overturning.

Both the Coal Mining Safety and Health Act 1999 and the Mining and Quarrying Safety and Health Act 1999 require the risks to be assessed and kept to within acceptable limits.

“Before using this type of vehicle, evaluate its suitability for the site and for the configuration planned,” the Queensland Mines inspectorate recommends.

“Operators should be trained and competent to operate the equipment.

“Particular care must be taken when operating fully articulated vehicles on cross slopes. Speed must be reduced to match the conditions.

“Take particular care when operating the vehicle as a water cart. Check the tank has baffles.

“Vehicles should not be overloaded.”