Main Roads – Reducing heavy vehicle rollovers

REDUCING HEAVY VEHICLE ROLLOVERS

Each year, across Western Australia, Main Roads sees a significant number of heavy vehicle rollovers. More concerning, however, is that with a number of inexperienced drivers recently entering the industry, rollovers are occurring more often.

Along with causing damage to goods, vehicles and road infrastructure, rollovers can result in loss of life. To help reduce this risk, it is important that drivers understand what causes them.

Road condition

Rollovers often occur on curves or at intersections, however, they can also occur if the rear trailer leaves the sealed road, particularly if there is a soft road shoulder or a drop off between the seal and the shoulder. This often happens when the driver is fatigued or distracted, so it’s important that you drive to the road conditions. Pay attention, slow down if the road is narrow and there are no sealed shoulders and anticipate curves to ensure they are entered at an appropriate speed. Do not accelerate through a curve and be careful not to be too abrupt with the steering.

Speed

Speed has a dramatic effect on vehicle stability and controllability. By increasing your speed from 30 km/h to 60 km/h you can increase the overturning forces by more than four times, and this is amplified through each trailer in a multi-trailer combination.

Centre of Gravity (CoG)

The higher the Centre of Gravity height of a load, the higher the rollover risk. Generally, if the CoG height of the load is more than 2.3 metres from the ground, the rollover risk is high. However, this is also then dependent on the mass of the load as the rollover risk increases as the mass increases (subsequently increasing the CoG height).

Moving or live loads, such as a bulk liquid in a tanker, livestock, concrete in agitators and poorly restrained loads, can also further increase the risk of a rollover.

Vehicle Maintenance

Poorly maintained braking systems, suspension systems and underinflated or worn tyres can have a detrimental effect on vehicle performance.

With most rollovers involving multitrailer vehicle combinations, it is evident that the rear trailer may commence rolling over before the driver even realises and has an opportunity to apply the brakes. Electronic Braking Systems (EBS) with a Rollover Stability System (RSS) can prevent this from happening, as the systems will sense the vehicle is at risk of rolling and automatically control the braking system to stabilise the vehicle.

Fatigue and Distraction

Driver fatigue and distraction monitoring systems can significantly reduce the risk of rollovers and other accidents. A number of systems are available, however, a system that is physically monitored so the driver can be contacted when fatigue or distraction events are detected, and assisted until they have safely stopped the vehicle, is the most effective.

It is important that transport operators provide their drivers with adequate training and develop appropriate processes to minimise rollover risk. Transport operators are encouraged to use the SRT calculator available on the Permits and Orders page at the Heavy Vehicles tab at www.mainroads. wa.gov.au to assess the rollover risk of each vehicle configuration and load.

The SRT calculator enables operators to either adjust the load accordingly or ensure there are suitable controls in place to mitigate any risks.

For further information please visit the Heavy Vehicles page at mainroads.wa.gov.au or call the Heavy Vehicle Help Desk on 138 486