This paper presents simulation modeling as a method for portraying the dynamic space-time interaction of offenders, victims, and potential guardians; and it is demonstrated by applying routine-activity theory to street robbery.
The findings from the example model of street robbery show support for the basic premise of routine activity theory, which is that crime rates will increase as time spent away from home increases. Although the absolute number of robberies fluctuated as parameters were changed, the relative relationship between increasing time spent away from home and the rate of street robberies remained significant. The building of the simulation model began with the identification of the most basic theoretical propositions of routine activity theory. The next step was to develop a conceptual diagram that captured both the essential constructs and how they were related to one another. The constructs and their relationships were then formalized so they could be coded in a computer program. There were two types of people in the model, civilians and police. Civilians had the roles of the three major elements of crime, i.e., offenders, targets (victims), and guardians (protectors). The fourth element, routine activity, was influenced by the amount of time an individual spent away from home and the network of streets available for travel. Once convergence occurred in space and time, factors such as guardianship and suitability of target were considered by the offender when making the decision about whether or not to commit a robbery. The model was built by using Agent Analyst software, which combines two of the most popular packages for agent-based modeling and geographic information systems. Although the model can be applied with any street network, the street network of Seattle, WA provided the basis for agent movement in the model. 6 tables, 4 figures, and 84 references