Hong Kongs roads have one of the highest vehicle densities in the world and its railways are among the most intensively utilized in the world. Associated with the existing and growing ransportation network are environmental pollution issues that require tackling at bothstrategic and local project level. Over recent decades, a series of Comprehensive Transport Studies and Railway Development Studies have formed the key blueprints for transport development in Hong Kong. This paper escribes the life-cycle of transportation projects in Hong Kong and presents how environmental inputs play a key role in the process, from Strategic Environmental Assessment (SEA) for territorial wide transport studies, through to project Environmental Impact Assessments (EIA), to Environmental Monitoring and Audit programs during project implementation. All these inputs aim to achieve a more sustainable transportation system.