Abstract
We build a system dynamics model based on a conceptual model originally proposed by safety scientist Jens Rasmussen to explore the dynamics of a safety system subject to pressures for performance improvement. Rasmussen described forces that generate a drift in the boundary of acceptable performance that can push the organization towards "flirting with the margin" and thus operate at very high risk of catastrophic safety failure. Simulations of the model faithfully replicate the behavior described by Rasmussen and others in a variety of scenarios. Simulation experiments further illuminate the potential for risky behavior and point towards some approaches to better system safety.