The New York City Police Department (NYPD), officially the City of New York Police Department, is the primary law enforcement agency within the City of New York. Established on May 23, 1845, the NYPD is one of the oldest police departments in the United States, and is the largest police force in the United States. The NYPD headquarters is at 1 Police Plaza, located on Park Row in Lower Manhattan across the street from City Hall. The NYPD's regulations are compiled in title 38 of the New York City Rules. The NYC Transit Police and NYC Housing Authority Police Department were fully integrated into the NYPD in 1995. The NYPD services include the Emergency Service Unit, K9, harbor patrol, air support, bomb squad, counter-terrorism, criminal intelligence, anti-organized crime, narcotics, public transportation, and public housing. There are also approximately 4,500 auxiliary police officers, 5,000 school safety agents, 2,300 traffic enforcement agents, and 370 traffic enforcement supervisors currently employed by the department. The Police Benevolent Association of the City of New York (NYC PBA), the largest municipal police unionin the United States, represents over 50,000 active and retired NYC police officers. Badges in the New York City Police Department are referred to as "shields" (the traditional term), though not all badge designs are strictly shield-shaped. Some officers have used "Pottsy" badges, "dupes," or duplicate badges, as officers are punished for losing their shield by also losing up to ten days' pay. Every rank has a different badge design (with the exception of "police officer" and "probationary police officer"), and upon change in rank officers receive a new badge. Lower-ranked police officers are identified by their shield numbers, and tax registry number. Lieutenants and above do not have shield numbers and are identified by tax registry number. All sworn members of the NYPD have their ID card photos taken against a red background. Civilian employees of the NYPD have their ID card photos taken against a blue background, signifying that they are not commissioned to carry a firearm. All ID cards have an expiration date.