  This paper draws on perspectives from co-design as an integrative and
collaborative design activity and co-simulation as a supporting information
system to advance engineering design methods for problems of societal
significance. Design and implementation of the Sustainable Infrastructure
Planning Game provides a prototypical co-design artifact that leverages the
High Level Architecture co-simulation standard. Three role players create a
strategic infrastructure plan for agriculture, water, and energy sectors to
meet sustainability objectives for a growing and urbaninzing population in a
fictional desert nation. An observational study conducts 15 co-design sessions
to understand underlying dynamics between actors and how co-simulation
capabilities influence design outcomes. Results characterize the dependencies
and conflicts between player roles based on technical exchange of resource
flows, identifying tension between agriculture and water roles based on water
demands for irrigation. Analysis shows a correlation between data exchange,
facilitated by synchronous co-simulation, and highly-ranked achievement of
joint sustainability outcomes. Conclusions reflect on the opportunities and
challenges presented by co-simulation in co-design settings to address
engineering systems problems.
