How does the geometry of a roadway (e.g., curves, grades) influence the selection of pavement surface treatments?

The geometry of a roadway, including curves and grades, significantly influences the selection of pavement surface treatments due to its impact on vehicle speed, braking forces, and stress distribution. Curves require vehicles to exert lateral forces, increasing stress on the pavement surface, particularly on the outside edge of the curve. High-friction surface treatments, such as chip seals with high-quality aggregates or microsurfacing, are often used on curves to improve skid resistance and reduce the risk of accidents. Grades, or inclines, affect vehicle speed and braking. Uphill grades cause vehicles to slow down, increasing the duration of loading on the pavement. Downhill grades require vehicles to brake, generating high shear stresses on the pavement surface. On steep grades, surface treatments that provide good wet weather friction and resistance to shoving (longitudinal displacement of the pavement surface) are essential. Intersections and areas with frequent braking also require high-friction surface treatments to prevent skidding and improve safety. Superelevation, the banking of a curve, influences the distribution of traffic loads across the pavement. Improper superelevation can concentrate traffic on one side of the roadway, leading to uneven wear and rutting. Surface treatments should be selected to address the specific distresses caused by the roadway geometry and traffic patterns. Areas with sharp curves and steep grades may require more frequent and more robust surface treatments than straight, level sections of roadway. Construction considerations also play a role. Applying certain surface treatments on steep grades or sharp curves can be challenging, requiring specialized equipment and techniques. In summary, roadway geometry is a critical factor in selecting pavement surface treatments, as it affects vehicle dynamics, stress distribution, and safety. Surface treatments should be chosen to provide adequate skid resistance, resist deformation, and improve safety in response to the specific geometric features of the roadway.