Stability assessment of agricultural tractors and self-propelled sprayers

Agricultural machines often work on rough terrain and sloping ground so instability and rollover events can easily occur. For agricultural tractors the solution adopted at international level was to provide them with Roll-Over Protective Structures (ROPS). Agricultural machines currently have to comply with the European Community (EC) 2006/42 Directive requirements and, if recognized as being at potential rollover risk, a protective measure for the driver has to be defined by the manufacturer. The aim was to analyse the safety of agricultural tractors and self-propelled sprayers. In particular, the research carried out concerned a tractor assessment of tractor by studying the effect of ROPS on the stability performance and the evaluation of the stability of self-propelled sprayers designed for arable crops according to the ISO 16231 procedure. In the tractor evaluation the results showed that the angle of lateral stability was not related to the mass even if, by fitting a cab ROPS, the position of the Centre of Gravity (CoG) had a negative influence on the angle of lateral stability. Considering the high percentage of accidents that occur when the foldable ROPS is fully lowered in the inoperative position, it is deemed preferable to have a tractor with a cab even if the stability limit angle is lower in the tractor configuration mounted with the cab ROPS. The stability assessment of two self-propelled sprayers, was carried out by determining the Static Overturning Angles (SOA) and by comparing it with the Required Static Stability Angle (RSSA). The evaluation showed that the risk of rollover and tipping-over is low for this machine type and no ROPS mounting was required. However, in reason of the ROPS experience on tractors, the compulsory installation of a ROPS on the self-propelled sprayers could produce a valuable reduction of accident rollover fatalities over the time.