This chapter examines performance within the context of a certain subtask, based on the task of human driving, for example. It explores the driving task into subtasks, and aims to define criteria that measure performance for the most meaningful subtasks. The chapter also aims to evaluate criteria for different human control strategy (HCS) models. Performance evaluation forms an integral part of HCS modeling research, without which it becomes impossible to rank or prefer one HCS controller over another. The chapter analyzes performance as a function of how well a particular HCS model is able to navigate tight turns. The solid line describes the road median, while the dashed line describes the actual trajectory executed by Harry’s HCS model. The specifications for HCS models normally include several time-response indices for specified input commands as well as desired steady-state accuracy.