Loose-Surface Tire-Terrain Interaction During High-Speed Maneuvers

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Loose-Surface Tire-Terrain Interaction During High-Speed Maneuvers

N. L. Buck / B. A. Coutermarsh / S. A. Shoop

For many years, rally-car drivers have been training military Special Forces in driving techniques that allow them to maintain high speeds on loose surfaces. The Cold Regions Research and Engineering Laboratory has been working with rally-car drivers to gain a more complete understanding of their driving techniques and their knowledge of driving on loose surfaces. This study was designed to quantify anecdotal descriptions of dynamic changes in the road surface as a result of successive high-speed maneuvers on a loose-surface roadway. The two primary maneuvers tested both involve a controlled skid on unpaved surfaces: the straight-line brake and high-speed hard turn. Multiple tests of each maneuver were completed over the same section of roadway on two different types of loose surface. Test observations showed that, as a vehicle traverses a section of roadway in a controlled skid, the tires remove loose material and transport the material to a new location, thereby changing the tractive characteristics of the roadway. This change is amplified as successive vehicles traverse the same path. A significant increase in the surface traction coefficient is observed where material has been removed from the original surface, and a decrease in surface traction is observed where loose material has built up on the original sur-face.