While under the influence of alcohol and other drugs, a driver's ability to divide attention is
the impaired driver tends to concentrate on only the
most important or critical parts of driving and disregard the
less important parts, often creating unexpected or dangerous situations for other drivers.
An impaired driver may
have difficulty in
steering, controlling the accelerator, signaling, and making decisions
(whether to stop, turn, speed up, slow down, etc.).
The second task is to observe the stopping sequence. The following questions may be helpful:
โข What is the vehicle doing?
โข Do I have grounds to stop the vehicle?
โข How does the driver respond to my signal to stop?
โข How does the driver handle the vehicle during the stopping sequence?
Your attention may be drawn to the vehicle by things such as it committing a traffic violation,
an equipment violation, having an expired registration, or making unusual driving actions such as weaving within a lane or moving at slower than normal speed.
The common effects of alcohol on the driver's mental and physical faculties lead to
predictable driving violations and vehicle operating characteristics. These include:
โข slowed reactions
โข impaired judgment as evidenced by a willingness to take risks
โข impaired vision
โข poor coordination (See Figure 11-2, below)
The National Highway Traffic Safety Administration sponsored research to identify the
most common and reliable initial indicators of DUI. This research identified ____ cues,
each with a high probability that the driver exhibiting the cue is impaired
The cues were developed from a list of more than _____ driving cues that have been found to predict alcohol concentrations of 0.08 or greater
occurs when the vehicle
alternately moves toward one side of the roadway and then the other,
creating a zigzag course. The pattern of lateral
movement is relatively regular as one steering correction is closely followed
Weaving Across Lane Lines
Extreme cases of weaving occur when the vehicle's wheels cross the lane lines before correction is made.
Straddling a Lane Line:
The vehicle is moving straight ahead with the center or
lane marker between the left-hand and right-hand wheels.
A swerve is an abrupt turn away
from a generally straight course. Swerving might occur after a period of
drifting when the driver discovers the
approach of traffic in an oncoming lane or discovers that the vehicle is going off the road. It may also occur as the driver executes an abrupt turn to return the
vehicle to the traffic lane.
Turning with Wide Radius:
During a turn, the radius defined by the distance
between the turning vehicle and the center of the turn is greater than normal. The
vehicle may drive wide in a curve.
Drifting is a straight-line movement of the vehicle at a slight angle to the
roadway. As the driver approaches a marker or boundary (lane marker, center line,
edge of the roadway), the direction of drift might change. Drifting can occur within
a single lane, across lanes, across the center line, or onto the shoulder
The observed vehicle almost strikes a stationary
object or another moving vehicle.
Almost Striking Object or Vehicle:
Stopping problems may include stopping abruptly or too far
from a curb, at an inappropriate angle, too short or beyond the intersection limit
line, or with a jerking motion.
Accelerating or Decelerating Rapidly
This cue encompasses any acceleration or
deceleration that is significantly more rapid than that required by the traffic
conditions. Rapid acceleration might be accompanied by breaking traction; rapid
deceleration might be accompanied by an abrupt stop.
The observed vehicle is traveling at a speed that is 10 mph or more below the speed limit.
Driving in Opposing Lanes or Wrong Way on a One-way Street:
The vehicle is heading into opposing or
crossing traffic by driving in the opposing lane, backing into traffic, failing to yield the right-of-way, or
driving the wrong way on a one-way street.
Slow Response to Traffic Signals:
The observed vehicle exhibits a longer than normal response to a change
in traffic signal.
Slow or Failure to Respond to Officer's Signal
The driver is unusually slow to respond to an officer's lights, siren, or hand signals.
Stopping in Lane for No Apparent Reason:
The critical element in this cue is that there is no observable justification for the vehicle to stop in the traffic lane.
Driving Without Headlights
The observed vehicle is being driven without headlights during a period of
the day when headlights are required.
Failure to Signal or Signal Inconsistent with Action:
This cue occurs when you observe inconsistencies such
as failing to signal a turn or a lane change, signaling opposite to the turn or lane change executed, signaling
constantly with no accompanying driving action, and driving with four-way hazard flashers on.
Following Too Closely:
The vehicle is following another vehicle while not maintaining the legal minimum
Improper or Unsafe Lane Change:
The driver takes risks or endangers others by frequently or abruptly
changing lanes without regard to other motorists.
Driving on Other than a Designated Roadway:
The driver maneuvers onto an area other than the designated roadway. Examples include driving at the edge of the roadway, on the shoulder, off the roadway entirely, or straight through turn-only lanes or areas.
Stopping Inappropriately in Response to an Officer
The vehicle stops in an inappropriate location, such as
a prohibited zone, crosswalk, intersection, or sidewalk, or under inappropriate conditions such as a green
or flashing yellow traffic signal.
Inappropriate or Unusual Behavior:
The driver or occupants display inappropriate or unusual behavior such
as throwing objects from the vehicle, drinking in the vehicle, or urinating on the roadside.
Appearing to Be Impaired:
This cue is actually one or more indicators related to the personal behavior or
appearance of the driver. Examples of specific indicators might include eye fixation, tightly gripping the
steering wheel, slouching in the seat, gesturing erratically or obscenely, holding face close to the
windshield, or protruding head from the vehicle.
5. Post-Stop Cues
An officer may observe any of the following behaviors in the driver after he or she stops the vehicle:
โข difficulty with motor vehicle controls
โข difficulty exiting the vehicle
โข fumbling with driver's license or paperwork
โข repeating questions or comments
โข swaying, unsteady, or having balance problems
โข leaning on the vehicle or other object
โข slurred speech
โข slow to respond to officer/officer must repeat questions
โข provides incorrect information, changes answers
โข odor of alcoholic beverage from the driver
6. Visual Detection of DUI Motorcyclists
NHTSA has also developed research identifying driving impairment cues for motorcyclists.
Excellent Cues (50% or greater probability that the driver is impaired)
โข drifting during turn or curve
โข trouble with dismount
โข trouble with balance at a stop
โข turning problems (e.g., unsteady, sudden corrections, late braking, improper lean angle)
โข inattentive to surroundings
โข inappropriate or unusual behavior (e.g., carrying or dropping object, urinating at roadside, disorderly
Good Cues (30 to 50 percent probability that the driver is impaired)
โข erratic movements while going straight
โข operating without lights at night
โข following too closely
โข running stop light or sign
โข going the wrong way
. After you give the command to stop, the impaired driver may exhibit additional important evidence of DUI. These observations may include the following:
โข an attempt to flee โข no response
โข a slow response โข an abrupt swerve
โข a sudden stop โข striking the curb or another object
Officers must be able to recognize evidence of impairment and describe that evidence clearly and
Once a vehicle is stopped, an officer should NOT ask a suspected impaired driver to
move to a safer location
The first task in Phase Two is a
face-to-face observation and interview of the driver
to determine if the driver may be impaired
in phase two the major decision is to
decide whether or not to ask the suspect to step out of the vehicle
At this point, there are three choices: (face-to-face)
: have the driver
exit, continue to interview the driver while observing for additional evidence, or conclude the interview if you
don't observe any impairment.
(phase 2) The second task is to observe the driver's exit and walk from the vehicle. Ask
yourself the following questions:
โข When I approach the vehicle, what do I see?
โข When I talk with the driver, what do I hear, see, and smell?
โข How does the driver respond to my questions?
โข Should I instruct the driver to exit the vehicle?
โข How does the driver exit?
โข When the driver walks toward the side of the road, what do I see?
DUI Detection Phase ______ comprises two major evidence gathering tasks and one major decision
observation and interview of the driverโbegins as soon as
both the subject
vehicle and the patrol vehicle have come to complete stops.
Face-to-face observation and interview of the driver allow you to use
three senses to gather evidence of alcohol
and other drug influence: sight, hearing, and smell.
Sight-Some specific DUI clues detectable by sight include
โข soiled clothing
โข fumbling fingers
โข alcohol containers
โข drugs or drug paraphernalia
โข bruises, bumps, or scratches
โข unusual action
You might hear these things during the interview, which would be describable clues or evidence of alcohol and
other drug influence:
โข admission of drinking
โข inconsistent responses
โข abusive language
โข unusual statements
Smel:l There are things you might smell during the interview that would be describable clues or evidence of alcohol and other drug influence. Typically these include the following examples:
โข alcoholic beverages
โข cover up odors like breath sprays
โข cigarette or cigar
Certain medical conditions may mimic drug- or alcohol-induced impairment:
such as epilepsy, diabetes, injury to the head, or cognitive problems (dementia or Alzheimer's).
A diabetic driver's behavior may be impacted, for instance, when
sugar levels are too high. At this time, his or
her breath could emit an odor similar to that of an alcoholic beverage or the driver could demonstrate a
comprehension or awareness problem
A driver's eyes can be examined for medical impairment. If his or her pupils are noticeably unequal in size, if the eyes are jerking as the subject looks straight ahead (resting nystagmus), or if the eyes do not track together, there is a chance that
a medical disorder or injury is causing the nystagmus.
The examinations that an officer
can conduct to assess possible medical impairment include noticing the following
โข resting nystagmus
โข tracking ability
is the ability of the eyes to track together when the subject attempts to follow a stimulus
moving side-to-side. The driver may have a medical condition or injury if the two eyes do not track together;
for example, if one eye has full range of motion, but the other moves only slightly or not at all.
divided attention task (driver still behind wheel)
the driver to concentrate on two or more things at the same time. They include both questioning techniques
and psychophysical tasks
PRE-EXIT INTERVIEWS These techniques are not as reliable as the Standardized Field Sobriety Tests,
but they can still be useful for obtaining evidence of impairment to establish probable cause.These techniques and the following Pre-Exit Tests do not replace the Standardized Field Sobriety Tests
The questions you ask and the way in which you ask them can constitute simple divided attention tasks.Three (3) techniques are particularly pertinent:
asking for two things in one request
โข asking interrupting or distracting questions
โข asking unusual questions
An example of the first technique, asking for two things in one request, is requesting that the driver produce
driver's license and the vehicle registration.
Possible evidence of impairment may come to light as the driver responds to this dual request. Be alert for the driver who:
โข forgets to produce both documents
โข produces documents other than the ones requested
โข fails to see the license, registration, or both while searching through wallet or purse
โข fumbles or drops wallet, purse, license, or registration
โข is unable to retrieve documents using fingertips
The second technique, asking interrupting or distracting questions, forces the driver to divide attention between searching for the license or registration and
answering a new question.
" Possible evidence of impairment may be disclosed by the interrupting or distracting question. Be alert for the driver who:
โข ignores the question and concentrates only on the license or registration search
โข stops searching to answer question, then forgets to resume the search after answering the question
โข supplies a grossly incorrect answer to the question
Use the third technique, asking unusual questions, after you have obtained the driver's license and registration.
With this technique, you seek verifying information through