Police Patrol-Initiated Activities Within a Systems Queueing Model

Officers in police patrol cars operate in a complex stochastic environment. In addition to handling dispatcher-assigned calls for service from the public, they patrol to pose a threat of apprehension to would-be offenders and undertake certain on-site interventions to help improve general public safety. The on-site work, often highly discretionary, is called patrol-initiated activity. It includes issuing tickets for traffic violations, building checks, car checks, pedestrian checks and assisting motorists. In many cities patrol-initiated activities and calls for service consume comparable amounts of officers' time. In this paper we develop a spatially-oriented queueing-type model of a police patrol force that allows each of N patrol cars to be in one of three states: (1) busy, on a call for service; (2) busy, on a patrol-initiated activity; (3) free, on patrol. Designed for computer solution, the model yields N nonlinear equations whose unknowns are the workloads of the N patrol cars. Other performance measures of patrol can be computed easily in terms of the workloads. The incorporation of patrol-initiated activities represents an improvement over previous OR/MS models, and could result in more informed police management decisions regarding patrol beat design, workload smoothing among officers, and reduction of neighborhood-specific inequities in police accessibility. The methods of this paper are potentially applicable to other urban services, including taxi and maintenance operations.