ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
In 1955, formulas for computing mobility indexes MI and converting them to vehicle cone indexes VCI, or minimum soil strength required for 50- pass go-no go, for current military wheeled and tracked vehicles were reported. Subsequent trafficability tests with vehicles having construction-equipment-type tires showed that the computed VCI did not agree closely with test results. To obtain data to determine whether the MI formula for self-propelled wheeled vehicles needed modification, field tests were run with small vehicles equipped with large, high-flotation tires, very large vehicles with very heavy wheel loads, and a few conventional vehicles. Main test purposes were to obtain data to determine experimentally 50-pass VCI for some untested vehicles and from these and other test results develop an MI formula for a wide range of vehicle weights and tire sizes. Although only 16 vehicles were tested, VCIs were determined for 20 vehicle types. To determine if VCI prediction could be improved, a statistical analysis was made on both the original and revised MI formulas using a multiple linear regression technique.