Engineering Control Technologies to Protect Operators in Agricultural All-Terrain Vehicle Rollovers.

HIGHLIGHTS Rollovers are the leading cause of injury and fatality in farm all-terrain vehicle (ATV) incidents. Engineering technologies to prevent rollovers or protect the operator in ATV crashes were reviewed in this study. The advances in safety for ATVs are correlated with improvements in stability, handling, and crashworthiness. Operator protection devices and crash notification systems can protect the operator in ATV rollover incidents. ABSTRACT. All-terrain vehicles (ATVs) are the second most common source of injury, following tractors, in U.S. agriculture. Rollovers are the leading cause of death in farm ATV incidents, constituting about 85% of ATV-related deaths. There is neither a significant practical solution for ATV rollover crashes in the U.S. nor standards and rules for implementing such a solution. Behavior-based control methods have been used for several decades but have reached their limit of success. Hence, engineering controls are needed to significantly decrease the severity of injuries in ATV rollover incidents (as in tractor incidents). In this study, engineering technologies to protect the operator in agricultural ATV crashes were reviewed. The discussion includes improving crash testing and stability ratings, evaluating static stability of ATVs, dynamic handling tests of ATVs, using automatic systems to notify first responders of a crash, and testing and applying operator protection devices. The available standards, rules, and recommendations related to these technologies around the world are also discussed.

Foldable rollover protective structures: Universal lift-assist design.

The numbers of agricultural tractor rollover fatalities occurring with foldable rollover protective structures (FROPS) in their lowered position are significant. Raising and lowering the FROPS is a time consuming and strenuous process, and operators often leave the FROPS in the folded-down position providing no protection during a rollover. The purpose of this project is to design, manufacture, and test a lift-assist mechanism to raise and lower the FROPS from the operator's seat. The lift-assist design is based on the FROPS actuation forces, FROPS and tractor dimensions, and ergonomics engineering standards [SAE J898/ISO 6682 and SAE J1814]. The design considered can be retrofitted and will not modify or compromise the FROPS structure. A universal lift-assist lever design has been constructed and successfully tested for three FROPS of different sizes meeting appropriate ergonomics engineering standards. The operator actuation forces were less than the 75 N allowable maximum, and within the zones of comfort and reach for the operator. The lift-assist design uses an energy absorbing torsional spring to accommodate heavier FROPS designs.

The Effect of Friction on Actuation Torques of Foldable Rollover Protective Structures.

The number of fatal tractor rollover accidents with an inoperative foldable rollover protective structure (FROPS) has increased sharply in recent years. Operators frequently leave the FROPS in the folded-down position after lowering the FROPS to pass a low overhead obstacle. One possible explanation for leaving the FROPS in the folded position is that raising and lowering the FROPS is a time-consuming and strenuous process. The actuation torques required to raise and lower a FROPS are not well known and may be influenced by friction. The actuation torques of ten FROPS from four different models were measured. One model FROPS was tested on seven different vehicles, and three models were tested separately. The dynamic and static (initiation and holding) actuation torques were measured to evaluate the effect of static and kinetic friction on actuation torque. The dynamic actuation torques were measured before and after greasing the FROPS. The proposed instruction to measure the actuation torque based on OECD Code 7 was evaluated. Results showed that friction has a significant effect on the measured actuation torque and can increase the actuation torque by up to 212%. The friction varies between FROPS of the same model, which is due to variations in the manufacturing, maintenance, and age of the FROPS. The friction force could be decreased by greasing the FROPS, and decreasing the friction increased the lowering resisting torques and decreased raising torques of FROPS. The measured actuation torque based on OECD Code 7 instruction (static holding) is not a constant value. The dynamic method is recommended for measuring FROPS actuation torques.

Developing and evaluating a finite element model for predicting the two-posts rollover protective structure nonlinear behaviour using SAE J2194 static test.

This research focuses on applying Non-linear Finite Element (FE) techniques to predict ROPS force-deflection curves under the simulated standardised static tests. The Society of Automotive Engineers (SAE) J2194 ROPS static standard test was selected for this study. According to the SAE J2194 standard, ROPS must be capable of absorbing predefined levels of energy under longitudinal (rear) and transverse (side) load tests before collapsing as well as avoiding large deformations that infringe upon the driver's clearance zone or leave the clearance zone unprotected. A nonlinear finite element approach was used to predict the response of two rear-mount two-post ROPS under simulated side and rear test conditions for Allis Chalmers 5040 and Long 460 tractors. The ROPS were designed with the Computer-based ROPS Design Program using a bolted corner bracket assembly to simplify the ROPS design process. The recommended FE model (ASTM, C3D10M, 0.01) was found to predict the ROPS performance deflection (RPD) with average error less than 10% compared to experimental test measurements. The FE model predicted the ROPS behaviour under rear loads more accurately than under side loads. The developed FE model based on measured stress-strain curves from test specimens was found to predict the ROPS behaviour more accurately than the FE models developed based on the Ramberg-Osgood material model.

Development and Evaluation of a Computer-Based ROPS Design Program.

Tractor overturn is the leading cause of agricultural fatalities in the U.S. Most of these fatalities can be eliminated using a rollover protective structure (ROPS) and a seatbelt. Unfortunately, not all agricultural tractors designed to support ROPS have ROPS designs. A computer-based ROPS design program (CRDP) was developed and successfully tested to provide quick and simple two-post, rear axle-mounted ROPS designs based on SAE Standard J2194. The program uses the tractor dimensions and mass to calculate the dimensions needed for ROPS components. Excel was used as the framework to provide the input, calculation, and ROPS drawing worksheets. Three ROPS (for Massey Ferguson 265, Long 460, and Allis Chalmers 5040 tractors) were designed and constructed using the CRDP. Static rear, side, and vertical tests were conducted based on SAE J2194 on two of the ROPS. All ROPS performance deflection (RPD) tests were less than the ROPS allowable deflection (RAD), indicating that the ROPS passed the static tests. The third ROPS was successfully mounted on the tractor axle housing within one hour, demonstrating the ease of installation using a bolted corner bracket design. Although the CRDP provided quick and simple ROPS designs, this program does not eliminate the requirement to conduct and pass the performance tests for ROPS designs specified in OSHA and SAE standards.

The Effect of Speed on Foldable ROPS Actuation Forces.

The number of fatalities caused by tractor rollovers has decreased in recent years, but the number of fatal tractor rollover accidents with a folded-down rollover protective structure (ROPS) has increased. Operating a ROPS-equipped tractor in low overhead clearance zones is difficult and sometimes impossible. The foldable ROPS (FROPS) was designed to solve the rigid ROPS problem, but lowering and raising a conventional FROPS is a time-consuming and strenuous process. After operators fold down a FROPS to pass a low overhead clearance zone, some prefer to leave it in the folded or inoperative position, increasing the risk of a rollover fatality. The actuation forces for raising and lowering a FROPS are not well known and may be influenced by actuation speed. A completely randomized block design with two blocks, five levels of speed, and multiple replications was conducted to investigate the effect of speed on actuation torque. The blocks were two sizes of tractor FROPS. The test included five levels of speed, including two levels of static measurement and three levels of dynamic measurement. A variable-speed motor system was used to control the speed for raising and lowering the FROPS. The actuation torque is a function of the FROPS upper part shape, dimensions, material density, turning acceleration, and friction. A theoretical model was developed to predict the actuation torque based on the FROPS shape, dimensions, and material density. For one ROPS, due to friction, the dynamic actuation torque was greater for raising and less for lowering than the theoretical torque. Indicator variable regression was used to analyze the effect of speed on actuation torque. Results showed that speed had a significant (p > 0.05) effect on actuation torque. Although there were statistically significant differences between the dynamic actuation torques, these differences were relatively small and negligible compared to the differences between the static torques.

Tractor ROPS and Stability Research: Introduction to this Special Issue.

Agricultural production has clearly benefited from the development of the tractor. The tractor provides a traction device and mobile power source. However, operating large equipment with high clearance on uneven ground leads to stability and overturn issues. Around the world, tractor overturns are still a leading cause of agricultural production fatalities. This special issue of the Journal of Agricultural Safety and Health focuses on recent research on tractor ROPS (rollover protective structures) and stability. Engineers and scientists in both Italy and the U.S. have been working on these topics, attempting to solve old problems and address rising issues. Understanding the factors leading to tractor instability, investigating the structures protecting the operator, and examining the continuous roll potential will all lead to increased operator protection and reduced fatalities.

Initial effects of light armored vehicle use on grassland vegetation at Fort Lewis, Washington.

Sustainable use of military training lands requires understanding and prediction of the effects of military vehicles on vegetation. We examined the initial impacts of an 8-wheeled, light armored vehicle (LAV) on grassland vegetation at Fort Lewis, Washington. The LAV drove replicate spiral paths at two starting velocities, 10.3 and 5.1 m s(-1). The disturbed width (width of ground impacted by the tires) increased as turning radius decreased, but was unaffected by vehicle velocity. An inverse-exponential model predicted disturbed width (r(2)=0.68) at all turning radii for both velocities combined. In low-velocity spirals, and for straight tracking (turning radius>40 m) and moderate turns (radius 20-40 m) in high-velocity spirals, all vegetation damage was imprint (plants flattened by wheels). During sharp (radius <20 m), high-velocity turns, most or all of the disturbed width was scraped free of surface vegetation and soil, which was piled to the outside of each tire track. Total plant cover (all species) was not affected by track curvature in low-velocity spirals, but decreased in the order straight tracking>moderate turns>sharp turns in high-velocity spirals. In low-velocity spirals, post-tracking cover of several plant growth forms (non-native species, perennial species, sod-forming grasses) was similar to pre-tracking cover, but in high-velocity spirals, post-tracking cover of these growth forms decreased in the order straight > or =moderate=sharp. Cover of native species and forbs decreased more in high- than in low-velocity spirals, but was unaffected by curvature. Pre- and post-tracking cover of annual species, bunchgrasses, and shrubs was < or =3%. The most severe vegetation damage caused by operation of wheeled LAVs on grasslands is associated with sharp, high-velocity turns.