  The outbreak of coronavirus disease 2019 (COVID-19) has led to significant
challenges for schools, workplaces and communities to return to operations
during the pandemic, requiring policymakers to balance individuals' safety and
operational efficiency. In this paper, we present our work using mixed-integer
programming and simulation for redesigning routes and bus schedules for
University of Michigan (UM)'s campus bus system during the COVID-19 pandemic.
We propose a hub-and-spoke design and utilize real data of student activities
to identify hub locations and bus stops to be used in the new routes. Using the
same total number of buses to operate, each new bus route has 50\% or fewer
seats being used and takes maximumly 15 minutes, to reduce disease transmission
through expiratory aerosol. We sample a variety of scenarios that cover
variations of peak demand, social-distancing requirements, and break-down
buses, to demonstrate the system resiliency of the new routes and schedules via
simulation. The new bus routes are implemented and used by all UM campuses
during the academic year 2020-2021, to ensure social distancing and short
travel time. Our approach can be generalized to redesign public transit systems
with social distancing requirement during the pandemic to reduce passengers'
infection risk.
