Pittsburgh Police hats with checkered bands, which are dark navy blue and gold in color, popularly known as the "Sillitoe Tartan" and named after its originator, Percy J. Sillitoe, Chief Constable of Glasgow, Scotland, in the 1930s. While the checkered band is a common police symbol in the United Kingdom, Australia and some European countries, the Chicago Police Department, Cook County Sheriff's Police, the Allegheny County Sheriff's Office, and the Pittsburgh Bureau of Police are the only police forces in the United States that have adopted it as part of their uniforms. As recently as July 1930, police were required to wear
Police equipped with sirens and flashing light bars to aid in making others aware of police presence. Unmarked vehicles are used primarily for sting operations or apprehending criminals without alerting them to their presence. Some police forces use unmarked or minimally marked cars for traffic law enforcement, since drivers slow down at the sight of marked police vehicles and unmarked vehicles make it easier for officers to catch speeders and traffic violators. This practice is controversial, with for example, New York State banning this practice in 1996 on the grounds that it endangered motorists who might be pulled over by people