The first thing to understand in a DUI case is why the police make contact with a driver. Through the International Association of Chiefs of Police (IACP) and the National Highway Transportation Safety Authority (NHTSA), a division of the US Department of Transportation, a series of “driving clues” get recognized as indications that a person may operate under the influence. When a trained police officer sees one of these driving clues, it gives the officer a reasonable suspicion to continue with an investigation. The clues can go in five distinct categories. These include maintaining lane position, vigilance, braking, speed, and judgment.

Straddling center or lane marker65%
Appearing to be drunk60 %
Almost striking object or vehicle60%
Driving on other than designated roadway55%
Slow speed (more than 10 mph below limit)50%
Turning with wide radius over50%
Stopping (without cause) in traffic lane50%
Following too closely45%
Tires on center or land marker45%
Braking erratically45%
Driving into opposing or crossing traffic45%
Signaling inconsistent with driving actions 40%
Stopping inappropriately (other than in lane)35%
Turning abruptly or illegally35%
Accelerating or decelerating rapidly30%
Headlights off30%

Maintaining Lane Position

Maintaining lane position tends to be difficult for impaired drivers. A driver under the influence has an erratic driving pattern and several events can identify them to the police. Drifting, weaving, swerving and wide turns can identify an impaired driver quickly. Drifting happens when moving in a forward direction, but with a slight angle. Many times the driver will drift towards the centerline or the median slowly. Then, they correct the problem and begin to drift in the opposite direction.

Weaving is when a car moves side to side from one lane to another usually moving around other vehicles. When a person under the influence operates a vehicle, they can weave. This can happen even without the presence of other vehicles. Another sign of an intoxicated driver is one who comes extremely close to other objects. Drivers under the influence also tend to make wide turns. The driver may travel into the other lane when initiating the turn or while making it.


A driver’s vigilance is their ability to be aware of their surroundings. It also includes their ability to be alert and take notice of their environment to react appropriately. Driving into oncoming traffic and inconsistent signaling are two vigilance problems that can indicate driver intoxication. Driving into oncoming traffic occurs because the driver is not aware of their surroundings or alert to traffic signs.

Improper signaling also indicates intoxicated driving. A disoriented driver may signal and then turn in the opposite direction. This action is easily visible to officers of the law and other drivers signaling that there is a problem. According to former New Jersey State Trooper and DUI expert Gary Aramini, driving at night without headlights is one vigilance problem. This is a very common action of drunk drivers. Their vision is usually impaired and they do not even notice that they do not have their headlights on.


Oftentimes, an intoxicated driver can be viewed easily by the way that they stop their vehicle. Abrupt stops are a key sign as well as stopping too far from or beyond the line on the road. Stopping too far from objects or hitting objects such as parking blocks or parking in spots at improper angles also indicate an intoxicated driver.


Slow speed can be enough reasonable suspicion to pull over a driver. Speeding is not a typical sign of drunk driving because driving at faster speeds requires faster reflexes which an intoxicated driver does not possess. Vehicles moving at slow or extremely slow speeds along with varying speeds such as slowing down and then speeding up can determine drunk driving. Oftentimes, however, the initial contact with a driver is the result of an officer citing speeding as a reason for the initial stop of the arrested person.


Many times the judgment of a driver gets impaired when driving under the influence of alcohol or drugs. Illegal turns such as turning when a “no turn on red” is marked or turning and driving on one way streets or medians are judgment problems that often occur when a driver is under the influence. Driving on anything other than designated roadway can also indicate DUI.

Keeping the roads safe is a primary task of police officers, especially the officers on duty in the late evening and early morning hours, the high time for DUI arrests. If they determine that there is a possibility that a driver of a motor vehicle is impaired, they will not hesitate to pull the driver over and investigate further. If you get detained, always remember to act polite.

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