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A highway patrol is either a police unit created primarily for the purpose of overseeing and enforcing traffic safety compliance on roads and highways, or a detail within an existing local or regional police agency that is primarily concerned with such duties.
Duties of highway patrols or traffic police may include the following:
- Accident investigation: Gathering evidence to determine the cause of a roadway accident.
- Commercial vehicle enforcement: Enforcing highway laws related to commercial transport, including weight limits and hazardous materials rules.
- Education: Providing public information, handouts, and displays to encourage safe driving and usage of the roads.
- Emergency response: Securing the scene of a traffic accident by using cones and flares as well as providing first aid to the injured.
- Law enforcement: Assisting local police in rural areas, and keeping an eye out for non-traffic violations.
- Maintenance: Observing and reporting damage to the roadways, and conducting hasty road surveys after disasters or the passage of inclement weather.
- Traffic enforcement: Enforcing laws and regulations intended to improve traffic safety, such as speed limits.
In Australia, traffic policing is the responsibility of the state police forces. Each force has its own traffic sections, often a local section in each area and a statewide section.
- Australian Capital Territory: Traffic Operations (territory wide)
- New South Wales Police Force: Traffic & Highway Patrol Command (statewide)
- Northern Territory Police: Highway Patrol Unit (territory wide)
- Queensland Police Service: Traffic Branch (local), State Traffic Task Force (statewide)
- South Australia Police: Traffic Services Branch (statewide)
- Tasmania Police: Traffic Division
- Victoria Police: Highway Patrol (local), State Highway Patrol (statewide)
- Western Australia Police: Highway Patrol (local), Traffic Enforcement Group (statewide)
In Brazil, traffic policing is the responsibility of state and federal police forces accordingly to the highway administration status. State administered highways (usually shorter, within state borders, two-way, single lane, lower traffic) are policed by a branch of the Military Police forces, called State Highway Military Police. At the same time Federal highways and roads (longer, crossing state borders, some double lane and high-traffic) are the responsibility of the Federal Highway Police.
There is also a third police force in Newfoundland known as the Royal Newfoundland Constabulary, which serves several metropolitan areas. Although this police force no longer exists as the main provincial police service, it is in competition with the Royal Canadian Mounted Police for the role.
Currently, the provincial sheriffs' service in Alberta maintains a highway patrol that shares traffic duties with the Royal Canadian Mounted Police and historically, several provinces, e.g. New Brunswick, have had their own highway patrols. Quebec also operates the Contrôle routier Québec, who enforce traffic laws in relation heavy vehicles.
In France, traffic policing on highways is the responsibility of dedicated units of the Gendarmerie Nationale (France), the Escadron départementaux de sécurité routière (EDSR) and the CRS autoroutières of the National Police (France).
In India, traffic policing on highways are carried out by state police forces.
- Andaman and Nicobar Police
- Andhra Pradesh Police
- Arunachal Pradesh Police
- Assam Police
- Bihar Police
- Chandigarh Police
- Chhattisgarh Police
- Dadra and Nagar Haveli Police
- Daman and Diu Police
- Goa Police
- Gujarat Police
- Haryana Police
- Himachal Pradesh Police
- Jammu and Kashmir Police
- Jharkhand Police
- Karnataka Police
- Kerala Police
- Lakshadweep Police
- Madhya Pradesh Police
- Maharashtra Police
- Manipur Police
- Meghalaya Police
- Mizoram Police
- Nagaland Police
- Orissa Police
- Pondicherry Police
- Punjab Police
- Rajasthan Police
- Sikkim Police
- Tamil Nadu Police
- Tripura Police
- Uttar Pradesh Police
- Uttarakhand Police
- West Bengal Police
In Japan, the Traffic Bureau of the National Police Agency (Japan) licenses drivers, enforces traffic safety laws, and regulates traffic. Intensive traffic safety and driver education campaigns are run at both national and prefectural levels. The bureau's Expressway Division addresses special conditions of the nation's growing system of express highways.
In the Netherlands, policing on the highways falls under the purview of the Dienst Verkeerspolitie (transportation police), which is one the Korps landelijke politiediensten (national police services, as opposed to the regional forces).
In Spain, traffic policing on highways is the responsibility of the Civil Guard (Spain), except in the autonomous communities with transferred competences on traffic policing (Catalonia and the Basque Country), where regional police forces (Mossos d'Esquadra and Ertzaintza, respectively) are responsibly for this area. In Navarra, traffic policing is shared between the Guardia Civil and the regional police (Policía Foral de Navarra).
- Police Scotland: Trunk Roads Patrol Group and Divisional Road Policing Units
- Central Motorway Police Group: Staffordshire Police, West Mercia Police, and West Midlands Police
- Devon and Cornwall Police, Road Policing Unit
- Essex Police, Road Policing Unit
- Greater Manchester Police, Road Policing Unit
- Hampshire Constabulary, Road Policing Unit
- Metropolitan Police Service, Road Policing Unit
- North West Motorway Police Group: Cheshire Constabulary, Lancashire Constabulary, and Merseyside Police
- South Wales Police, Road Policing Unit
- Surrey Police, Road Policing Unit
- Thames Valley Police, Road Policing Unit
Many state police agencies in the United States take the name of "highway patrol" rather than "state police". State police agencies may fulfill the role of highway patrol, and vice versa. For instance, the California Highway Patrol is actually a state police agency, meaning that it is a police body having statewide authority to conduct law enforcement activities and criminal investigations. In addition to its highway patrol duties described above, it performs functions outside the normal purview of the city police or the county sheriff, such as enforcing traffic laws on state highways and interstate expressways, overseeing the security of the state capitol complex, protecting the governor, training new officers for local police forces too small to operate an academy, providing technological and scientific support services, and helping to coordinate multi-jurisdictional task force activity in serious or complicated cases. The California Highway Patrol also serves as bailiffs and courtroom deputies for certain state courts, such as the appellate courts and the California Supreme Court building in San Francisco. The state traffic enforcement agency retained the name "California Highway Patrol" after the merger of the smaller California State Police with the larger—and better-known—CHP and the combination of their functions into one agency.
However, some Highway Patrol organizations, such as the North Carolina State Highway Patrol are specifically charged with the enforcement of traffic laws, and while able to enforce other laws, they are not official "state police" agencies in the same vein as the California Highway Patrol or the New Jersey State Police. In other cases, states like Texas have a bona fide and appropriately named state police department such as the Texas Department of Public Safety, of which only one arm is a highway patrol division. In addition, the police departments of Boston, New York City, and Philadelphia have highway patrol units. A privately compiled list of Highway Patrol organizations and similar state police agencies is available on the web. The Iowa State Patrol maintains a list of phone numbers and * and # cell phone numbers for non-emergency calls to the dispatchers of the Highway Patrol organizations in all 50 states. These numbers are useful for motorists who want to report aggressive driving, driving under the influence, or other dangerous but not life-threatening situations that do not require a 9-1-1 call.
Highway patrol and state police officers are often referred to as "state troopers". Historically, a troop was a small cavalry unit; many state police forces originated as mounted paramilitary forces who were stationed in barracks like soldiers, hence the term "trooper." A state trooper goes by the title "trooper", as in "Trooper John Smith". Some agencies, particularly on the east coast, refer to their state police offices as "barracks," although troopers generally do not reside there. Other state police forces, particularly highway patrols as in California, have always modeled themselves after police officers who simply commute to work like ordinary civilians. Like police officers, they use the title "officer."
- Alabama Highway Patrol
- Alaska State Troopers
- Arizona Department of Public Safety
- Arkansas State Police
- California Highway Patrol
- Colorado State Patrol
- Connecticut State Police
- Delaware State Police
- Florida Highway Patrol
- Georgia State Patrol
- Idaho State Police
- Illinois State Police
- Indiana State Police
- Iowa State Patrol
- Kansas Highway Patrol
- Kentucky State Police
- Louisiana State Police
- Maine State Police
- Maryland State Police
- Massachusetts State Police
- Michigan State Police
- Minnesota State Patrol
- Mississippi Highway Patrol
- Missouri State Highway Patrol
- Montana Highway Patrol
- Nebraska State Patrol
- Nevada Highway Patrol
- New Hampshire State Police
- New Jersey State Police
- New Mexico State Police
- New York State Police
- North Carolina State Highway Patrol
- North Dakota Highway Patrol
- Ohio State Highway Patrol
- Oklahoma Highway Patrol
- Oregon State Police
- Pennsylvania State Police
- Rhode Island State Police
- South Carolina Highway Patrol
- South Dakota Highway Patrol
- Tennessee Highway Patrol
- Texas Highway Patrol
- Utah Highway Patrol
- Vermont State Police
- Virginia State Police
- Washington State Patrol
- West Virginia State Police
- Wisconsin State Patrol
- Wyoming Highway Patrol
*Hawaii is the only state without an agency that provides statewide uniformed patrol. 
- "Constabulary Website". Retrieved 27 January 2012.
- "NC Department of Crime Control and Public Safety". Nccrimecontrol.org. Retrieved 2009-06-11.
- Terrance D. Martin. "Official Directory of State Patrol and State Police". Statetroopersdirectory.com. Retrieved 2009-06-11.
- "Iowa State Patrol Division - Emergency Contacts While Traveling in Iowa". Dps.state.ia.us. 2009-05-19. Retrieved 2009-06-11.