Abstract:
This study represents a collaboration between the Colorado Department of Transportation and the Colorado auto insurance industry to analyze the costs associated with using sand as a traction agent on roadways during winter. The research investigates two main areas: the cost of sanding to CDOT, including materials, labor, and equipment; and the cost to the public due to vehicle damage, specifically to windshields. The study highlights a shift in CDOT's winter maintenance policy from heavy reliance on a sand-salt mixture to an increasing use of deicing chemicals, a change linked to improved air quality and a reduction in airborne particulate matter (PM-10). To understand the mechanism of windshield damage, the project conducted laboratory and field tests using a high-speed camera to record the motion of airborne particles. A key finding from these tests was that sand particles become airborne vertically after a tire rolls over them due to the release of stored strain energy. This mechanism was verified through a finite element analysis (FEA) using the implicit NIKE3D code. The FEA simulated a particle-pavement interaction by applying a vertical impact load to a particle resting on a pavement model, providing insights into how recoil velocity is influenced by the material properties of both the particle and the pavement. The study concludes that the shift in maintenance policy has likely contributed to a reduction in windshield damage claims, although sand use remains necessary for safety. It recommends an optimal winter maintenance strategy that balances the use of sand and deicing chemicals and calls for further research on the physical factors affecting the particle airborne mechanism.
