Icarus is a simulation developed by Arizona State University and the University of California Los Angeles to estimate the effects of environmental hazards on travelers and indoor activities, and evaluate the efficacy of mitigation strategies. Icarus was developed by a team of engineers, environmental scientists, and public health scientists. It combines a state-of-the-art agent-based travel simulation (MatSIM), an indoor exposure model, environmental hazard models, and infrastructure data to estimate the effects of environmental disturbances in cities. The simulation is able to evaluate neighborhood to city-scale effects. Its initial uses have included assessing heat exposure mitigation, travel behavior changes due to roadway disruptions, and the effects of infrastructure changes on personal comfort during travel.