This publication guides authorities to implement and maintain nuclear transport security regimes effectively. This publication provides detailed guidance to States and their competent authorities on how to implement and maintain a nuclear security regime for the transport of nuclear and other radioactive material. The publication builds upon relevant recommendations in NSS No. 13 and NSS No. 14 and provides additional explanations of how to implement these recommendations in practice. This publication is intended for nuclear security regulatory bodies and may also be useful to operators, shippers, carriers and others with transport security responsibilities to design their transport security systems.