Sustainability is based on a simple principle: Everything that we need for our survival and well-being depends, either directly or indirectly, on our natural environment. Sustainability creates and maintains the conditions under which humans and nature can exist in productive harmony, that permit fulfilling the social, economic and other requirements of present and future generations.

Sustainability is important to making sure that we have and will continue to have, the water, materials, and resources to protect human health and our environment.

The purpose of North-Star is to identify the characteristics of a sustainable transit corridor and to develop tools, procedures and techniques that can be incorporated into standard planning, design and construction practices to make each transit corridor more sustainable. It is intended that North-Star guide our collective knowledge of sustainability principles and criteria, as well as techniques to provide guidance in best sustainable design..