Sustainability assessment is now emerging as a more transparent, comprehensive, integrated and far-sighted approach to decision making. Its basic demand is that all significant undertakings must make a positive contribution to sustainability. To apply this test, decision makers need criteria based on the core requirements of sustainability and the particularities of the context. As well, they need appropriately designed public processes; guidance on the weighing of alternatives, trade-offs and compromises; a supportive policy framework; suitable tools and inspiring examples.