Rapid urbanization, with new construction estimated to be 250 times NYC by 2050, is increasing traffic congestion, pollution and related health threats. This is a worrisome development but also a unique opportunity to improve urban mobility and quality of life. Understanding consequences of urban design choices on mobility, sustainability, and health is a necessity and requires development of a framework that enables such co-design processes. We propose a new design-toolkit to incorporate mobility, sustainability, health, and thermal comfort metrics into urban design projects. Process accuracy and impact is validated in collaboration with leading design practitioners and the NYC Planning Department.