To be effective, police forces must be in close proximity to the citizens they serve. The first and most basic means of maintaining that close contact was the foot patrol. Officers were deployed by time of day (watches) and area (beats). Beats were kept geographically small to allow officers to respond to incidents in a timely manner. In larger rural jurisdictions, officers were deployed on horseback. Both foot and mounted patrols continue to be used throughout the world. Foot patrol is used in congested urban areas, in high-density housing complexes, and at special events; mounted patrol is also used for special events and for crowd control.

Foot and mounted patrols were followed by bicycle patrol, which spread throughout continental Europe at the end of the 19th century. Bicycle patrol made a comeback in the late 20th and early 21st centuries as a compromise between foot and car patrols. Bicycle patrol officers are specially trained and equipped with robust but lightweight urban bicycles. Bicycles are very useful for patrolling urban parks, housing complexes, school campuses, and locations where there are multiple large walkways not immediately accessible from the street.

The development of the automobile in the late 19th century dramatically transformed police work in the early 20th century. The city of Akron, Ohio, U.S., claims to have deployed the first automobile police patrol wagon in 1899. The vehicle was powered by an electric battery, however, which greatly limited its range over distances. A motorcycle patrol was instituted in New York City in 1905. By 1910 in France, 12 regional mobile brigades of police had become fully motorized; they used gasoline-powered automobiles manufactured by the De Dion-Bouton company to crisscross France. The motorization of police forces took place simultaneously in virtually all Western countries; by World War I, many urban police departments were using motorized patrols. Automobiles allowed police to expand patrol beats and reduced the time required for responding to incidents. However, the mobility and speed that police cruisers provided came at the expense of police visibility, as officers were increasingly encapsulated in their cars.

The police cruiser played a bigger role in the cities of the New World—Australia, Canada, New Zealand, and the United States—than elsewhere. New World cities generally were laid out in a gridlike pattern with large intersecting avenues that facilitated motorized police patrols. By contrast, European cities typically featured a maze of small, crowded streets that required foot patrols. The equipment carried by the standard police vehicle in these New World cities significantly evolved from the 1970s to the early 21st century. In the 1970s the police car was basically the same as the mass-produced vehicles owned by citizens. It was fitted with few accessories for enhancing comfort, such as air conditioning, and the specific police equipment that it carried consisted of a two-way radio with limited capacities and an external rotating light fitted on its roof; a metal screen between the front and the back seats was common but not standard. By the 21st century, the modern big-city patrol vehicle was routinely fitted with heavy-duty alternators to power numerous electronic devices and a powerful cooling system to handle engine heat while idling during hot weather. It also was equipped with an array of electronic devices, including radios, siren and light controls, a public-address system, a cellular telephone, a radar unit to measure motorists’ speed, and, in many jurisdictions, a mobile digital terminal for access to police databases. Even the trunk was filled with equipment, such as first-aid and biohazard-response kits. Like the police vehicle itself, such equipment reflects the technologies produced by domestic industries. In countries whose industrial sectors are large and technologically advanced, such as the United States, Germany, and Japan, police cruisers tend to be very sophisticated instruments; elsewhere, they are more rudimentary.

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The array of duties performed by police today requires a variety of different vehicles, ranging from minicars to buses and fully equipped mobile headquarters. For example, traffic-law enforcement is often conducted by patrol officers on motorcycles, but cars also are commonly used. In the United States, police often drive sport-utility vehicles (SUVs) for highway patrol. Police cruisers are generally smaller in Europe and Japan than in the United States and Canada, reflecting the standards of domestic auto industries. In Germany and Italy, police may use sophisticated sports cars, such as Porsches, BMWs, and even Ferraris, for high-speed chases.

Some police vehicles have been adapted from military vehicles. Police in South Africa use the Buffel, a vehicle derived from an armored personnel carrier, and the Police Service of Northern Ireland (formerly the Royal Ulster Constabulary) uses military vehicles in its patrols. In the United States, some police departments have converted armored scout vehicles to assist in high-risk operations. Vehicles built on large chassis can be used to transport a fully equipped command center to a crime scene or disaster area.

The environment is another factor that determines the types of vehicles used by police forces. In many rural jurisdictions the typical four-door sedan has been replaced by SUVs and four-wheel-drive trucks. In areas where there are no paved roads (e.g., open country, beaches, and forests), the police use all-terrain vehicles and off-road motorcycles. Snowmobiles and tracked vehicles are used in areas where large snow accumulations are typical.

Police departments that patrol waterfronts employ small to midsize open-cockpit motorboats. Customs and border-surveillance agencies have access to some of the most complex and exotic watercraft to combat illicit drug-running and border incursions. In areas with large swamps, the police use airboats (flat-bottomed boat hulls with an aircraft engine and propeller for propulsion).

Various types of aircraft are used in police patrols as well. Helicopters, the most common type, are often equipped with a high-intensity spotlight that can provide overhead illumination for units on the ground. Another device used by aircraft, a passive infrared unit sometimes called forward-looking infrared (FLIR), provides night vision. FLIR units can measure the heat energy emitted by objects and living things, enabling ground units to be directed to a particular location. The police also employ fixed-wing aircraft for operations such as border patrols and drug surveillance, police-personnel transport over long distances, and highway traffic control. They range in size from single-seat planes to multiengine jet aircraft.

Communication

The vehicles discussed above would be nothing more than efficient conveyances if police officers were unable to communicate instantly with each other and the public. In the earliest police forces, communication was accomplished through oral or written orders in an administrative chain of command. As society progressed, the military was used less for domestic peacekeeping. Depending on whether a country evolved toward more or less centralization, systems of national or local control were established. In England the watch-and-ward system evolved to provide citizens with protection from crime. During times of duress, the men on watch would raise the hue and cry to summon assistance from the citizens of the community or, in the case of a larger community, from others already on watch. The watch standers were equipped with various signaling devices, including bells, ratchets, and rattles.

With the passage of the Metropolitan Police Act in 1829, the police in England were formalized into a full-time paid service, as they had been in France, Austria, and Prussia. The system was directed by a central command through face-to-face contact between supervisors and subordinates. As urban areas expanded and the police were deployed to more beats over larger geographic areas, this system of human communication became increasingly inefficient. Face-to-face contact gave way to the use of telegraphs in the mid-19th century, and in the late 1870s police departments began installing telephone systems. In urban jurisdictions call boxes, or street telephones, were placed on beats to enable patrol officers and citizens to alert the central command of disturbances. In 1937 the first emergency telephone system was established in London, where callers could dial 999 to speak to an operator.

Early systems of police dispatch involved a single operator who took calls from the public and dispatched officers via radio. In 1917 the police department of New York City began equipping patrol vehicles with a one-way radio receiver that enabled the central command to send emergency messages to officers. However, that and other early radio-communications systems were fraught with technical problems. In 1928, following several years of experimentation, the police department of Detroit improved the technology to allow regular contact between headquarters and patrol units; the system developed in Detroit was subsequently the basis of police communications systems used throughout the United States. Two-way radio receivers were first deployed in 1933 in Bayonne, N.J., and their use proliferated in the 1940s. Radios in patrol cars were eventually supplemented by portable radio transceivers carried by individual officers to allow uninterrupted radio contact between officers and the dispatch center. Dispatch was improved in the United States in the late 1960s with the establishment of the 911 emergency telephone system. Similar systems have since been adopted in other countries throughout the world.

Police radio-communications systems benefited from the development of computers, which made possible the quick retrieval of information on stolen property, wanted persons, and other police intelligence. Computers were eventually placed in patrol cars. These mobile digital terminals (MDTs) enable officers to check licenses, wanted-persons lists, and warrants from the patrol vehicle without making an oral radio transmission. MDTs have been supplemented with a wide variety of digital pagers and cellular phones.

Computerization

The police were early adopters of computer database technology. In the United States the National Crime Information Center (NCIC) was established in 1967; police records were subsequently computerized and made available to police agencies throughout the country. The NCIC’s database enables local police departments to apprehend offenders who might otherwise evade capture. The database contains fingerprints, a registry of sexual offenders, and mug shots, and it can be queried for detailed information on stolen vehicles and warrants for firearms violations; it can even search for phonetically similar names. Similar databases maintained by U.S. states provide police with access to misdemeanor warrants, driver-citation records, and vehicle-ownership information.

The European Union (EU) established a computerized information system—the Schengen Information System (SIS)—which allows the authorities of certain member states, plus some other European countries, to send or receive data about criminals, missing persons, stolen property, and other matters of interest to law enforcement officers. Each member of the EU, however, must devise its own computerized system to connect to the SIS. The European Police Office (Europol) also maintains a computerized database. In addition, Interpol manages databases of fingerprints, DNA profiles, and information on stolen property and other matters, which member countries can retrieve through a global police- communications system known as I-24/7.

Computer-assisted-dispatch (CAD) systems, such as the 911 system in the United States, are used not only to dispatch police quickly in an emergency but also to gather data on every person who has contact with the police. Information in the CAD database generally includes call volume, time of day, types of calls, response time, and the disposition of every call. The Enhanced 911 (E911) system, adopted in the United States, instantly identifies the number of the phone from which the call is made, as well as the name and physical address of the person who owns the phone. Data maintained in the E911 system sometimes include a history of calls to the police from the caller’s location. When the CAD system is linked to a global positioning system (GPS), dispatchers can immediately identify the police cruiser nearest the scene of the emergency.

Although records are essential for effective police operations, police departments would be overwhelmed without a mechanism for filtering information and making sense of it. Police have long been able to gather information from related cases by using whatever records were available to them, but, until the advent of computerized databases, such cases could be found only through the recollection of experienced investigators. Computerized records systems can be extremely effective in drawing out relationships between past and present cases and suspects. The computer acts like a seasoned detective with an encyclopaedic memory. Systems known as Compstat (see above Compstat), used by a variety of large cities, enable police departments to piece together information and to deploy personnel efficiently.