This report documents the research efforts undertaken to design, construct, and test rollover protective structures (rops) and to develop rops performance criteria for large mobile mining machines. The following tests were conducted: two rollover tests of a 52,000- pound machine, two rollover tests and one static test of a 390,000- pound machine, and one rollover test of a 286,000-pound machine. The tests were conducted on a specially constructed hill with a slope of 35 deg and were designed to provide consistent and repetitious results. Each roll test was designed to provide a minimum of 540 deg of machine rotation about the longitudinal axis, allowing the rops to impact the slope twice. Using data obtained from the testing, as well as all other available rollover data in which rops loading and energy absorption characteristics were known, recommended performance criteria were developed, including side force and energy, longitudinal force, and vertical force.