Health impact assessment (HIA) has emerged in the U.S. as one promising process to increase social and environmental justice through addressing health equity issues within planning. HIA practice is guided by values such as democracy and equity and grounded in broad social determinants of health. The most readily applied definition of democracy is problematic because it implies an element of direct, participatory engagement with the public. This is at odds with HIA practice that largely relies on stakeholder engagement strategies. This dissertation critically examines the engagement strategies of three transportation planning HIA cases to more fully understand how the HIA process may or may not promote democratic values and protect community health interests. It employs a multi-case study design that uses qualitative content analysis to trace community health interests through the HIA process, HIA document, and target plan. It finds that while the field is overstating the participatory nature of HIA, commitments to health equity and broad determinants of health protect community health interests with and without robust engagement of community stakeholders.