Turning Problems
The research also identified four turning problems that indicate rider impairment:

• Unsteady During Turn or Curve. The gyroscopic effects of a motorcycle’s wheels tend to keep a motorcycle “on track” as long as speed is maintained. As a motorcycle’s speed decreases, the demands placed on the operator’s balancing capabilities increases. As a result, an officer might observe a motorcycle’s front wheels or handlebars wobbling as an impaired rider attempts to maintain balance at slow speeds or during a turn.
  
  
• Late Braking During Turn. The next turning problem is “late braking during a turn or on a curve.” A motorcyclist normally brakes prior to entering a turn or curve, so the motorcycle can
  accelerate through the maneuver for maximum control. An impaired motorcyclist might misjudge the speed or distance to the corner or curve,
  requiring an application of the brakes during the maneuver.
  
  
• Improper Lean Angle During Turn.
  A third turning problem occurs when a motorcyclist normally negotiates a turn or curve by leaning into the turn. When a rider’s balance or speed decision-making is impaired, however, the rider frequently attempts to sit upright through the maneuver. As a result, a trained observer can detect an “improper lean angle.”
  
  
• Erratic Movements During Turn.
  The fourth turning problem is “erratic movements.” These are defined as an inconsistent action or a sudden correction of a motorcycle maneuver during a turn or curve that can also indicate impaired driving. If you observe a motorcyclist who is unsteady during a turn or curve, brakes late, assumes an improper lean angle, or makes erratic movements during a turn or curve, there is a better-than-average chance that the motorcyclist is driving while impaired.

Inattentive to Surroundings
Vigilance concerns people’s ability to pay attention to a task or notice changes in their surroundings. A motorcyclist whose vigilance has been impaired by alcohol consumption might fail to notice that the traffic light has changed from red to green.

A vigilance problem also is evident when motorcyclists are inattentive to their surroundings or are seemingly unconcerned with detection by law enforcement.
For example, there is cause for suspicion of DWI when a motorcyclist fails to
periodically scan the area around the bike when in traffic, a wise defensive riding measure to guard against potential encroachment by other vehicles. There is further evidence of impairment if a motorcyclist fails to respond to an officer’s emergency lights or hand signals.

If you observe a motorcyclist to be inattentive to the surroundings, there is a better than average chance that the motorcyclist is a DWI violator.