Piezoelectric energy-harvesting systems are a promising way to convert mechanical energy from the environment into usable electrical power. This review examines the key factors, methodologies, and recent developments in designing and improving these systems to increase efficiency and power output. It covers the principles of piezoelectricity, material properties, system design, and optimization strategies including frequency tuning, circuit design, and MPPT. Challenges such as low output, environmental sensitivity, and scalability are discussed along with potential solutions. The study also explores future trends such as smart grid integration and self-powered IoT. This review contributes valuable insights for advancing renewable energy through smart pavement applications.