Alcohol affects both the brain and body, impairing key functions required to safely operate a vehicle. As a depressant, alcohol slows brain activity, reduces attention, and disrupts coordination, making driving dangerous. Even moderate alcohol consumption can narrow a driver’s visual field and slow reactions to changing road conditions.
What Is DUI/DWI?
- DUI: Driving Under the Influence of alcohol or other drugs.
- DWI: Driving While Intoxicated or Driving While Impaired.
Variations by State
Terminology varies by state:
- DUI may refer specifically to alcohol use.
- DWI may include alcohol, drugs, or unknown substances.
- Some states charge DWI if the driver shows severe impairment even below the legal BAC limit.
Prevalence of Drunk Driving
- In 2012, 29.1 million Americans admitted to driving under the influence.
- In 2006, 18,000 people died in alcohol-related crashes (≈40% of all traffic fatalities).
- Drivers with a BAC of 0.10% are 9 times more likely to cause a fatal crash than sober drivers.
How Alcohol Impairs Driving
Alcohol affects multiple driving skills, increasing accident risk.
Tracking
Difficulty maintaining proper lane position.
Reaction Time
Slower responses to hazards or sudden changes in traffic.
Impairment of the Senses
Reduced vision and perception, particularly when scanning the road or judging distances.
Judgment
Poor decisions on speed, distance, and vehicle maneuvers.
Concentration
Difficulty multitasking or responding to multiple stimuli simultaneously.
Blood Alcohol Concentration (BAC) Levels
The CDC categorizes BAC into levels:
- 0.02% – minor judgment impairment
- 0.05% – reduced multitasking ability, relaxation
- 0.08% – legal limit for most non-commercial drivers
- 0.10% – impaired visual function, poor judgment
- 0.15% – severe impairment, high crash risk
Federal DUI Laws
- Apply on federal property: military bases, airports, national parks, and government buildings.
- First-time offenses are misdemeanors, punishable by up to 12 months in jail or fines.
- Commercial drivers: legal BAC limit is 0.04%, stricter than non-commercial drivers.
State DUI Laws
- BAC limits, definitions, and penalties vary by state.
- Zero tolerance applies for drivers under 21.
- Refusing chemical tests (breath, blood, urine) often results in license suspension.
Example BAC Limits
| Driver Type | Most States | Notes |
|---|---|---|
| Non-commercial 21+ | 0.08% | Legal limit |
| Commercial | 0.04% | Stricter for safety |
| Under 21 | 0.01–0.02% | Zero tolerance in many states |
DUI Arrest Rates by State
- Highest per capita: Wyoming (1.17%), Idaho (0.78%), Alaska (0.75%)
- Lowest per capita: Washington D.C. (0.01%), Delaware (0.03%), Illinois (0.03%)
High rates are often linked to lightly populated states with less severe penalties, while low rates occur in densely populated states with stricter laws.
DUI Investigation and Arrest Procedures
Observation
Police monitor driving behavior for erratic movements such as weaving, sudden braking, or inconsistent signaling.
Reasonable Suspicion
A valid traffic violation or suspicious behavior must exist to justify a stop.
Probable Cause
Once reasonable suspicion is established, officers gather evidence via:
- Field sobriety tests
- Confessions or admissions
- Breath or blood tests
Testing Procedures
Field Sobriety Tests
- One-Leg-Stand Test
- Walk-and-Turn Test
- Horizontal Gaze Nystagmus Test
Preliminary Alcohol Screening
Portable breath tests provide immediate BAC estimates before formal chemical testing.
Chemical Tests
Blood, urine, or breath tests confirm BAC and detect possible drug use. Refusal can lead to license suspension under implied consent laws.
Criminal Charges and Court Procedures
- Charges depend on BAC, observed impairment, and prior offenses.
- Arraignment: formal reading of charges; defendant enters plea.
- Remand: pre-trial detention for high-risk suspects; most are released on bail or own recognizance.
DUI Prevention Strategies
- Ignition Interlocks – prevent cars from starting if BAC is above 0.02%.
- Sobriety Checkpoints – allow police to legally stop vehicles and test drivers.
- Mass Media Campaigns – educate on alcohol dangers and legal consequences.
- Alcohol Screening – identify at-risk individuals and offer treatment.
- License Suspension – revoke licenses for refusal or exceeding BAC limits.
- School-Based Programs – teach young people the risks of drunk driving.
