This project is designed to provide a public resource for supporting simulation work with split belt treadmills or other asymmetric ground contact conditions such as variable surface stiffness. Walking on single- or dual-belt treadmills can be simulated by assigning ground contact geometry to moving bodies controlled by coordinate actuators and assigning tracking goals to these walking platforms. Project includes OpenSim models and Moco scripts to enable optimal control simulations of split belt treadmill walking.