The key process parameters influencing asphalt modified polyurethane in bitumen modification include temperature, mixing time, and shear rate. Higher temperatures enhance the dispersion of polyurethane in asphalt, while optimal mixing time ensures uniformity. Shear rate affects the viscosity and stability of the modified asphalt. Additionally, the ratio of polyurethane to asphalt and the presence of additives can significantly impact the performance characteristics, such as elasticity, adhesion, and resistance to aging.