over three decades during which policy requirements for safety featureson tractors were first
introduced and then later strengthened. The incidence of fatal andnonfatal tractor rollover
injuries was compared with the proportion of farm tractorswith and without rollover protective
structures (ROPS) at different times from the late1950s up to 1990. From the period 1957-
1964 to the period 1986-1990 rollover fatalities decreasedfrom 12 to 0.2 per 100,000 farm …