Health Impact Assessment (HIA) is a systematic process to evaluate the potential health impacts of any plan, project or policy before implementation and has recently started gaining traction in the transportation sector as well. HIAs also recommend appropriate corrective or preventive measures to manage the health impacts of the proposed plan or policy. Transportation HIAs can take place at any level, from site to corridor, city, regional, and national. HIAs could be led by the private, public, or voluntary sector.
HIAs differ widely in scope, depth, and level of public engagement but they usually follow six broad steps: Screening, Scoping, Assessment, Recommendations, Reporting and Montoring and Evaluation. 
This image (source: cdc.gov) appears in EMBARQ’s issue brief, Integrating Health Benefits into Transportation Planning and Policy in India. For a detailed Health Impact Assessment framework and a pilot application quantifying health impacts of air pollution, traffic injuries and fatalities, and physical activity, refer to the EMBARQ India Issue Brief on Integrating Health Benefits into Transportation Planning and Policy in India.