Context: 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 impersonating police officers.

Question: When do police often use unmarked cars?
Answer: primarily for sting operations or apprehending criminals without alerting them to their presence

Question: What use of unmarked cars is controversial?
Answer: for traffic law enforcement

Question: When did New York State ban unmarked cars for traffic cops?
Answer: 1996

Question: Why did New York State ban unmarked cars for traffic cops?
Answer: it endangered motorists who might be pulled over by people impersonating police officers

Question: When do police often use marked cars?
Answer: Unanswerable

Question: What use of unmarked cars isn't controversial?
Answer: Unanswerable

Question: When did New York State ban marked cars for traffic cops?
Answer: Unanswerable

Question: Why did New York State allow unmarked cars for traffic cops?
Answer: Unanswerable

Question: Why did New York State ban marked cars for traffic cops?
Answer: Unanswerable