The key role of infrastructure planning is ensuring that decisions related to infrastructure investments take into account needs, trade-offs, political priorities and long-term development goals, and do so in a transparent and consultative way. This approach works well for projects where private interests can accurately estimate future demand. However, for sectors and projects where market mechanisms may not be feasible or appropriate (e.g. as a result of non-excludability or externalities), a greater degree of planning becomes necessary.