Computer-aided dispatching (CAD) systems were developed in the 1960s as part of the first major wave of police department computerization (Colton 1978). By the mid-1980s CAD had become nearly universal in medium and large-sized police departments (Hickman and Reaves 2002a; McEwen et al. 2002). By the late 1990s CAD systems were used to a lesser extent by sheriff’s offices and local police departments. In these agencies computers were used for managing calls for police services by 47% of sheriff’s offices and 32% of local police departments (Hickman and Reaves 2003b). Today, along with 911 emergency call systems, CAD systems are the primary information technology supporting police communications centers in almost all medium and large-sized police departments.
The first generation of CAD systems was developed to manage the calls for service and the dispatching functions of police departments (Colton, Brandeau, and Tien 1983). These systems were designed to monitor large fleets of patrol units and calls for service, to centralize the patrol function, and to reduce the response time of patrol units to citizens’ requests for assistance (Colton, Brandeau, and Tien 1983). These systems were also intended to operate as online work order systems that kept track of calls for police assistance and coordinated these calls with available patrol units (McEwen et al. 2002; Pierce, Spaar, and Briggs 1988).
To support the goal of coordinating requests for assistance and patrol units, a CAD system operates by first defining a set of items/data that call-takers collect when they receive requests for assistance. The CAD system then transfers the call-taker information to a police dispatcher’s computer screen who has responsibility for the geographic area associated with the request for assistance. The CAD system provides information to the dispatcher on available patrol units and recommends a unit(s) to dispatch to the request for assistance. The dispatching recommendations are usually based on a set of rules/guidelines, such as patrol unit availability, location of the incident, and type of request for assistance (McEwen et al. 2002). Finally, CAD systems also often collect information from the patrol unit(s) responding to requests for service regarding the disposition of the request and availability of the unit(s) for service.
The central role of CAD systems in police communications centers makes it possible for these systems to collect and computerize a broad range of public safety-related data for police departments. The computerization of calls for service data is a product of CAD systems’ ability to track and store digitized data on the actions and activities of call trackers, police dispatchers, and patrol units responding to request for assistance. Based on a national survey of police departments, McEwen et al. (2002) found that the range of data routinely collected (and also often computerized) by CAD systems includes data on (1) requests for police assistance (for example, time, location, and nature of problem or incident as identified by individuals requesting assistance), (2) police officer responses to requests for assistance (for example, time of dispatch, arrival, and completion of service), (3) recorded comments between responding officers and dispatchers, and (4) information on the disposition of the request for service (for example, office provided final disposition information, formal incidents reports, data on additional responding units, arrest reports). Importantly, many CAD transactions between callers, dispatchers, and patrol units are essentially time stamped by the CAD system and addresses are typically verified by the CAD system’s geographic database.
Although CAD systems have successfully enabled police to more systematically manage calls for service and patrol unit dispatching, earlier generations of CAD systems also may have caused police to think too narrowly about the potential uses of CAD systems (Dunworth 2000). First-generation CAD systems (with little reserve computing capacity to support other law enforcement functions) encouraged many police departments to focus on one of the primary performance indicators these systems routinely generated— response time—at the expense of other less easily measured performance indicators, such as fear of crime (Gruber, Mechling, and Pierce 1991). In addition, the introduction of CAD systems along with the implementation of the 911 emergency call systems in the 1960s and 1970s both supported and encouraged the centralization of police services and the professional model of policing, thus rapid response became a primary strategy for addressing serious crime (Maguire 1997; McEwen et al. 2002). Finally, the advent of CAD systems combined with the emergence of 911 emergency phone systems in the early 1970s provided the technological foundation for the development of the preventive patrol emergency response strategy of policing in major American cities during the 1970s and 1980s.
During the last two decades, however, CAD systems have evolved to support potentially a much broader range of law enforcement strategies and tactics, including problem-oriented policing and community-oriented policing strategies, which rely on a more proactive approach to policing. CAD systems have evolved to incorporate ”intelligent” decision support capabilities that can triage requests for assistance based on call priorities, manage multiple unit dispatches, coordinate with fire and emergency medical services, link to criminal history inquiry systems and/or motor vehicle registry systems, and support mobile digital terminals in patrol units (Gruber, Mechling, and Pierce 1991; McEwen et al. 2002). As a result, current CAD systems often incorporate a broad range of data that is important to dispatchers directing the calls and to officers responding to calls (Morgan 2003).
A major challenge for the future development of CAD systems lies in the more productive use of the data that these systems collect to support more proactive policing tactics and strategies. A major national study of the potential of CAD systems to support community policing identified several areas where CAD data are either underutilized or need significant enhancement (McEwen et al. 2002). The study concluded that future CAD systems should increase the scope (for example, collect data on officer time devoted to problem solving, expand call classification schemes to incorporate data on community concerns and perceptions) and precision (for example, refine call classification schemes), and that CAD systems need to continue to increase links with other sources of public safety information. The report also concluded that CAD data must become more accessible to potential users (for example, patrol officers, crime analysts, police supervisors, and administrators), and that there is a need for a greater application of CAD to problem-solving tactics and strategies.
Finally, as CAD systems continue to evolve, they also need to coordinate with (and take advantage of) advancements in other types of law enforcement-related technologies. These include advances in global positioning systems (Casey et al. 1996) and geographic information systems, and evolving applications for wireless communications (Douglas 2004; Dunworth 2000; Diemert 2005).
