Sustainable transport is safe, high-quality, and accessible to all, ecologically sound, economically viable, and a positive contributor to local, national and international sustainable development. Economic, social and environmental sustainability can only be achieved through an integrated inland transport system. When water, road and rail transport work together, the comparative advantage of each mode can be exploited optimally. Creating an efficient integrated transport network requires international collaboration. The United Nations Regional Commissions provide platforms for intergovernmental cooperation and address the sustainability of transport, across its five key areas – accessibility, affordability, safety, security, environmental impact – through a variety of legal instruments, analytical work and technical assistance, as well as through their governance structures.