Safety nets form an integral part of the ATM system, so much so that they can sometimes be taken for granted; however, as the environment within which they operate evolves, safety nets need to be continuously improved to remain effective. This requires sustained efforts to optimise and improve them, as well as commitment from the wider organisation. This Guide, first produced in 2011, has been reissued following the update of the EUROCONTROL guidelines on safety nets published in January 2017. It provides additional context complementing the information provided in the guidelines. Particular focus is given to the action areas for effective safety nets and the safety nets life cycle.