The purpose of this chapter is to provide an overview of microsimulation concepts and methods that may be used in travel-related forecasting applications. Including this very brief introductory section, the chapter is divided into eight sections. Section 12.2 defines the term
. Section 12.3 discusses the reasons why microsimulation may prove useful or even necessary for at least some types of activitybased travel forecasting applications. Section 12.4 defines the important concepts of objects, agents, and cellular automata, which represent fundamental organizing constructs in modern microsimulation models. Section 12.5 discusses a key step in the microsimulation process — synthesizing and updating the attributes of the population or sample of individuals whose behavior is being simulated. Section 12.6 then discusses some of the major issues associated with the development and application of operational microsimulation methods, while Section 12.7 provides representative examples of transportation-related microsimulation applications. Finally, Section 12.8 presents several microsimulation models drawn from a range of applications, including activity-based travel forecasting.