Mainstreaming Green Infrastructure Elements into the Design of Public Road Reserves: Challenges for Road Authorities

摘要

lobal warming poses particular challenges for urban areas due to the greater intensity of rainfall and issues of stormwater runoff, and the heat island effect generated by the reflection of the sun off hard surfaces, such as buildings and road pavements; for example, in Australian cities (i.e., Sydney), roads account for approximately 25% of all urban land use. The challenge for road authorities is to implement green infrastructure in road planning, design and implementation as the term “green infrastructure” has appeared increasingly throughout the world in land management and planning. Despite these environmental challenges, traditional highway engineering practices use arguments regarding the economic inefficiencies of urban traffic congestion to justify the business case for road-widening schemes and new road construction projects with associated de-forestation and vegetation loss. An international literature review and site visits of green infrastructure best practice in Australia, Singapore, the U.K. and the USA is reported. A typical road authority project is described in Sydney, Australia, where the initial design concept to accommodate growth in all modes of transport was road widening and land acquisition, but the authors persuaded the local and state government authorities to consider other options to “green” the infrastructure, particularly opportunities to add trees and vegetation near the roadway, which provide the additional bonus of managing surface water runoff. From this general problem, the case for, and value to, road authorities to develop green infrastructure guidelines for project planning and implementation, are presented. The conclusions include ongoing research to formulate draft guidelines for governments based on a holistic approach to the planning and design of high-density urban development around transport nodes that includes green infrastructure principles.