Abstract
Keywords- ATV, Safety, ROPS, Injury, Risk-Benefit, ISO 13232
The injury benefits and risks as related to the feasibility of Rollover Protection Systems (ROPS) for All Terrain Vehicles (ATVs) were analyzed by means of full-scale tests and computer simulations based on a sample of 113 real ATV accidents from the UK and USA, and by adapting and applying the methods of ISO 13232 for motorcycle rider protective devices. A review of previous research on this subject is presented. A computer simulation model of an ATV, rider (an ISO Motorcycle Anthropometric Test Device (MATD) crash dummy, with and without helmet) and terrain was developed, based on the requirements of ISO 13232. Rider injury criteria included the 8 body regions specified in ISO 13232 (2005), plus skull fracture criteria. Five ROPS designs (i.e., the Dahle, Johnson, T-Bar, U-Bar, and MUARC ROPS) were modelled and fitted to the baseline mid-size ATV. Hardware prototypes of the U-bar and T-bar ROPS were constructed and fitted to a baseline ATV. Twelve instrumented full-scale rollover tests were conducted and high speed filmed with the baseline ATV, and U-bar and T-bar ROPS, in order to quantitatively calibrate the accuracy of the simulation models against real rollover events. 113 UK and US ATV accidents were then simulated with the baseline ATV and with each of the 5 ROPS configurations, with and without a rider helmet. The change in injury severity and frequency due to each ROPS concept was quantified across the sample of simulated accidents, and expressed in terms of the injury benefits and injury risks due to the ROPS, according to ISO 13232. The risk-tobenefit percentages of the ROPS devices were compared to one another and to other automotive and motorcycle safety devices. It was found that, on a small, high-mobility vehicle such as an ATV, the ROPS designs examined caused more injuries than they prevented. The conclusion was that for such small, "straddle-seat" vehicles, restraining the rider to the vehicle can be injurious, due to two injury mechanisms. These were: transmitting large g-forces to the rider (in cases where the rider is tightly restrained to the vehicle) or introducing severe ROPSto- rider impacts (in cases where the rider is not restrained or loosely restrained to the vehicle). In addition, adding a ROPS on such a small vehicle substantially raised the center of gravity of the vehicle, adversely affecting stability. Use of a helmet by the rider of the baseline ATV has far lower risks and far greater benefits than any of the ROPS alternatives. In addition, it is suggested that avoiding (rather than adding) rigid external projections on the ATV is an important priority for increasing ATV safety. The results reported are significant for the design and planning of ATV rider protection strategies and for ATV design engineering. The results also suggest the usefulness of a standard like ISO 13232 being developed for ATVs and for other small, dual-track vehicles, in order to facilitate feasibility studies of other rider protection strategies.