A random traffic stop is conducted at the discretion of a law officer. The driver of a vehicle is temporarily pulled over so police can investigate possible crimes or infractions of the law. United States law states that a police officer needs only a reasonable suspicion that a crime is in progress or about to occur to perform a random traffic stop. A random stop is accomplished by the police using a siren, lights, or a loudspeaker to get the driver's attention. Once the driver is aware of the police he is expected to pull over to the side of the road in a safe manner. Some random stops result in the arrest of a suspect. This occurs when the occupant of the car is wanted for a crime or the random stop reveals a criminal action. During the stop the police will check to see if the driver has any outstanding warrants before a ticket or warning is issued.