What is sustainable urban infrastructure?

The "H" light rail line, 18th and California streets, downtown Denver. Rail-based public transport is an essential part of sustainable urban infrastructure. When combined with other modes such as walking or bicycling, rail transit enables people to efficiently meet individual transport needs in a healthy and low-impact manner.

Urban infrastructure is comprised of the complex systems designed to provide for resource delivery and to meet the needs of daily life for people in an urban setting. Urban infrastructure relies on development, so to conceptualize sustainable urban infrastructure, it is important to understand the idea of sustainable development. Gro Brundtland's classic definition of sustainable development is:

Development that meets the needs of of the present without compromising the ability of future generations to meet their own needs.

Sustainability, as it pertains to urban infrastructure, must conform to Brundtland's definition. This is not a simple task. Cities require ready access to enormous amounts of a high number of varied resources, from building materials to fuel to food. This is of great importance, because as of right about now, urban populations are overtaking rural populations in number for the first time in human history. More people now live in cictes than in the countryside. This fact makes a focus on pursuing sustainable objectives in regard to urban infrastructure a paramount issue.

An city is not a closed system, requiring outside imports to exist. In an urban environment, virtually any action has the potential to produce consequences which may affect the population at large. To achieve urban sustainability, it is necessary reduce the importation of energy and materials to as little as possible, while minimizing the generation of adverse effects and byproducts, while taking steps to remediate adverse production that cannot be avoided. Since urban inhabitants are completely dependent on infrastructure throughout the course of their everyday lives, it is absolutely essential to remove as much inefficiency in delivery of goods, services and utilities as possible, and to seek out and eliminate wasteful practices.

In the history of industrialization, material efficiency of delivery has taken a back seat to Keynesian economic goals and perceived convenience. The infrastructure of western industrialized urban cultures has been shaped by forces that rarely found it necessary to consider sustainability in infrastructure, as more of whatever in demand could always be imported, regardless of expense. It is only recently that as a society we have been forced to become aware of the inherently unsustainable characteristics of our system. As a culture, we are now increasingly motivated to focus on adaptive technological and behavioral changes necessary to continue to meet our needs while not inhibiting the prospects of future generations.