breathalyzer test) by invoking an implied consent request. While state terminology regarding whether evidentiary testing is an "arrest", such testing is constitutionally a "search incident to arrest". Procedure A stop is usually accomplished through a process known as "pulling over" the suspect's vehicle. Police vehicles (except those used by undercover personnel) traditionally have sirens, loudspeakers, and lightbars that rotate or flash. These devices are used by the officer to get the attention of the suspect and to signal that they are expected to move over to the shoulder and stop. Failure to comply could result in citation of failure to yield to an emergency vehicle and possibly raise suspicion that the driver is attempting to flee. Similar alerting devices are also typically equipped on other emergency vehicles such as fire trucks and ambulances, although police departments often use blue lights to signal drivers to pull over. In all cases, such signals and the laws requiring that other vehicles pull to the shoulder allow the emergency vehicles to pass other traffic safely and efficiently when responding to emergency situations. In the case of a traffic stop, the officer pulls the patrol vehicle behind the subject vehicle as it stops instead of proceeding past as he or she would during other emergency responses. Depending upon the severity of the offense which the officer believes to have occurred, the officer may either arrest the suspect, by taking him or her to jail, or check for any outstanding warrants before issuing a citation also called a notice to appear or summons in some jurisdictions, which is essentially a traffic ticket. In some cases, officers may choose to simply issue a verbal or written warning. Many states have enacted laws requiring freeway traffic approaching the police vehicle to merge over to the left, leaving an entire lane as a buffer zone for the officer. A "felony" or "high-risk" traffic stop occurs when police stop a vehicle which they have strong reason to believe contains a driver or passenger suspected of having committed a serious crime, especially of a nature that would lead the police to believe the suspects may be armed (such as an armed robbery, assault with a weapon, or an outstanding felony warrant for the registered owner). In a high risk stop, officers attempt to provide their own safety by issuing instructions to maintain absolute control over every step of the proceedings. They