When critical decisions turn out badly, they harm, cripple, or kill businesses and careers. This book explains why critical decisions go awry in terms of the Law of Unintended Consequences, drawing on economics, cognitive psychology and complexity theory.  It then presents a novel simulation-based method for “test driving” decisions that helps leaders avoid "train wrecks" and achieve their intended outcomes. Four examples illustrate the method in action, supporting decisions about competitive strategy, disruptive growth, enterprise risk management, and enabling organizational change.