Although the basic principle of seatbelts operation has changed little since their introduction as mandatory equipment, the continuous integration of seat belts with other safety systems has created new challenges in their design, testing, and evaluation. This study provides an experimental investigation into the dynamic mechanical behaviour of seat belt webbing, with particular emphasis on its energy dissipation capacity under impact conditions. Novel aspects of this work include a comparative evaluation of new belts and intentionally degraded belts, enabling a phenomenological assessment of how defects influence load response and potential injury risk. Energy characteristics were employed as comparative indicators, providing an interesting complementary diagnostic measure. Dynamic impact tests were performed using a high-speed camera system to capture displacement-time histories, and mathematical functions approximating the experimental data were proposed with strong agreement to measurements. The results highlight underexplored differences in webbing performance under defective conditions, providing new insights relevant to regulatory compliance and the development of advanced restraint systems.