The fourth edition of Road Safety Manual (RSM) developed by the World Road Association (PIARC) is designed to help countries at every stage of infrastructure development to fulfil road safety objectives. It is aligned with key pillars for the United Nations Decade of Action for Road Safety 2021-2030: Pillar 1: Multimodal transport and land use planning, Pillar 2: Safe Road Infrastrucure, Pillar 4: Safe Road Use. This comprehensive resource builds on the broad range of knowledge and experience provided by PIARC in the previous editions. It includes new thinking on road safety and offers a clear argument on why adopting a Safe System approach is crucial for all countries.