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ROPS IN LIGHT VEHICLES INING ROLL-OVER PROTECTION STANDARDS FALL FLAT Many commercially available ROPS are based on motorsport ROPS in terms of material and construction techniques. However, there are enough significant differences in light vehicle ROPS installations to question the validity of this approach, writes Doug Gould. Supplementary Roll-Over Protection (ROPS) is becoming a mandatory item for both company vehicles and contractor vehicles by an increasing number of mining companies. The requirement was initiated by Occupational Health and Safety (OH&S) committees responding to an incidence of roll overs with light vehicles. Initially, this requirement was met with whatever ROPS were available, frequently from engineering shops local to mine sites. However, now more critical consideration is being given to the design, manufacturing and test standards. So called “light vehicles” are the staple of mining fleets. These are the notional 1 tonne utility vehicles. Most are made in Thailand, e.g. Toyota Hilux, Mitsubishi Triton, Ford Ranger, Mazda BT50, Nissan Navara, Chevrolet Colorado, Isuzu Rodeo. This is one of the most competitive segments in the automotive world and there have been large improvements in ride quality and engine power in the last few years. This means that these vehicles have higher performance and can achieve higher speeds than in the past. Other 4WD vehicles on mine sites include Toyota Landcruiser, Nissan Patrol and Landrover Defender. However the smaller 4WDs are more common due to lower prices and they represent a greater challenge for ROPS because the cabin space is smaller and it requires more sophisticated ROPS designs to achieve the required stiffness and strength. In the mining context, higher speeds on poor roads are possible so that the potential of rollover is higher in the hands of undisciplined and/or fatigued drivers. This discussion is concerned only with above the ground vehicles. Below the ground vehicles have the additional requirements for falling object protection (FOPS) in addition to a range of other specialised modifications depending on the mine type. The above the ground vehicles drive on formed and unformed gravel roads within the mine and public roads to and from the mine accommodation and mine suppliers, etc. Contractor vehicles will be subject to the normal range of uses of private vehicles. The rollovers that we [Test-Trak] are accustomed to seeing are spectacular motor racing accidents. These rollovers can be high-speed high-energy events. Images and video of spectacular multiple turn rolls, sometimes involving the race car doing vertical pirouettes appear on TV, promotional videos and magazines. These images have not helped set the correct perception of the reality of mining operations in the minds of some of the people who set policy. The reality is that most rollovers associated with mining operations are relatively gentle events, but more on this later. The US government’s National Highway & Transport Safety Administration (NHSTA) have done extensive investigation of vehicle rollovers. It identified eight different types of vehicle rollover. In the mining context, the typical rollover occurs when the vehicle is “tripped” either on unformed clay roads (inside the mine site) or on gravel edge sealed roads (outside the mine). Gravel edge sealed road rollovers frequently occur due to driver inattention or fatigue causing the vehicle to move off the road surface the followed by an overreaction. These rollovers are typically relatively gentle (low speed and low “g”). This was investigated by Cooperider Hammond & Colwell (Characteristics of Soil Tripped Rollovers, SAE paper 980022) who describe a typical tripped rollover as occurring at approximately 60 km/h (after deceleration from highway speed from pre-event braking and skidding) with a roll rate of under 100 degrees per second and impact deceleration of under 1 “g”. Most mining rollovers are quarter-turn or half-turn rolls. In other words, the vehicle falls on its side or continues for a second quarter roll to come to rest on its roof. AUSTRALASIAN MINE SAFETY JOURNAL 61