Injury severity related to overturn characteristics of tractors

Early studies of injuries associated with overturns indicate that more fatalities occurred when a tractor overturned beyond 90 degrees (continuous roll) relative to the impact plane. Recently, the principle of preventing continuous rolls has re-emerged for the protection of riding lawnmower operators.

Related to tractors, a population-based study was conducted that compared the severity of fatal and nonfatal injuries between a 90 degrees and continuous roll for tractors equipped with rollover protective structures (ROPS) and not equipped with a ROPS (non- ROPS). In 2002, the Kentucky Farm Tractor Overturn Survey was administered to an 8% random sample (6,063) of Kentucky farm operators. The farmers responded to questions that differentiated between the types of overturns and operator injury outcomes for ROPS-equipped and non-ROPS tractors during overturn events. Overturn characteristics were collected that included 90 degrees to the side, beyond 90 degrees to the side, and to the rear for both ROPS-equipped and non-ROPS tractors.

Of the 541 overturns reported in this study, 535 (99%) of the respondents reported the most recent overturn characteristics of the tractor: 92 (17%) were ROPS-equipped and 443 (83%) were non-ROPS. For side overturns, 67% of the rolls occurred with ROPS-equipped tractors, and 54% occurred with non-ROPS tractors. The percentages of deaths related to rolls to the side for ROPS-equipped and non-ROPS tractors were, respectively, 1.6% and 3.7%. There was one (2%) deaths related to 90 degrees rolls for ROPS-equipped tractors, whereas for continuous rolls there were 6.4% fatalities related to side overturns, 13% resulted in non-fatal injuries with an average of 1 day of hospitalization for ROPS-equipped tractors, and 39% resulted in non-fatal injuries with an average of 18 days of hospitalization for non-ROPS tractors. The results from this study indicated that a ROPS was more effective at stopping an overturn at 90 degrees than no ROPS, with an associated reduction in the severity of injury in the event of a tractor overturn.