Impact assessment has been around for 50 years, since the American National Environmental Policy Act (NEPA) 1969 was enacted. It has become an internationally recognised approach to determining, in advance, the future consequences of projects on the human and ecological environments and how these impacts might be managed. Impact assessment is often described as a tool for determining risk to projects or disparaged as a regulatory barrier to approval. It is more usefully envisaged as reducing uncertainty, contributing to good planning and building community confidence in regulatory systems. These outcomes depend on good process: project definition, early scoping of technical and community issues and studies that are proportionate, purposeful, efficient and effective. In addition, good process means giving the community an influential voice in decision-making.