When a product is a complex dynamic system that interacts directly with a human, engineers must consider a wide range of possible motions and forces that the device could exert on the human. Such an analysis goes beyond a simple thought exercise and requires detailed knowledge about the system dynamics and the operating environment. This paper presents such an analysis of inverted-pendulum human transporters. The list of hazards is constructed by using knowledge of the dynamics and mechanical design obtained through simulation and experimentation. However, the dynamics are so complex that the list is augmented with hazards that are revealed by studying accident videos posted on the Internet. The severity of the hazards is estimated using an energy-based measurement of the hazard onset conditions as well as compounding factors from the mechanical design. In addition, experimental and simulation results of sample hazard conditions illustrate their danger and severity. The analysis reveals that inverted-pendulum human transporters have several hazards with unacceptable risk.

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