The particular duties of a police officer depend primarily on the jurisdiction in which they serve. In large cities, officers are typically assigned general job duties or are appointed to a department or unit that covers certain types of crimes, such as murder, fraud, rape, or drug-trafficking. These units have special objectives, and the officers within the unit are trained to investigate these specialized crimes. Officers in co-ops, townships, and other rural settings often handle all law enforcement tasks, from basic traffic infractions to home invasions to murder cases. The primary job of a police officer is to keep the neighborhoods and streets safe.