In the United States the National Highway Traffic Safety Administration (NHTSA) estimates that 17,941 people died in 2006 in "alcohol-related" collisions, representing 41 percent of total traffic deaths in the US. Over 500,000 people were injured in alcohol-related accidents in the US in 2003. NHTSA defines fatal collisions as "alcohol-related" if they believe the driver, a passenger, or an occupant of the vehicle (such as a pedestrian or pedalcyclist) had a blood alcohol content (BAC) of 0.01 or greater. NHTSA defines nonfatal collisions as "alcohol-related" if the accident report indicates evidence of alcohol present. NHTSA specifically notes that "alcohol-related" does not necessarily mean a driver or nonoccupant was tested for alcohol and that the term does not indicate a collision or fatality was caused by the presence of alcohol. On average, about 60 percent of the BAC values are missing or unknown. To analyze what they believe is the complete data, statisticians simulate BAC information.
Prior to increased emphasis on drinking and driving in the 1980s, standards of .10-.15 percent were in place. The legal limit for commercial drivers in the U.S. is set at 0.04 percent. All states also observe a much stricter standard for drivers under the age of 21, commonly of .01-.02; these are often referred to as "Zero Tolerance" laws.
Federal Air Regulation 91.17 (14 CFR 91.17) prohibits pilots from flying aircraft with an alcohol level of 0.04% or more, and/or within eight hours of consuming alcohol, and/or while under the impairing influence of any drug. The same prohibition applies to any other crewmembers on duty aboard the aircraft (flight attendants, etc.). Some airlines impose additional restrictions, and many pilots also impose stricter standards upon themselves. Commercial pilots found to be in violation of regulations are typically fired or resign voluntarily, and they may lose their pilot certificates and/or be subject to criminal prosecution under Federal or State laws, effectively ending their careers.
Unlike DUI, DWI, or OWUI cases that involve alcohol, there is generally no "per se" or legal limit that is employed for persons accused of driving under the influence of prescription medication or illicit drugs (although this is not the case in Ohio.) Instead, the key inquiry focuses on whether the driver's faculties were impaired by the substance that was consumed. The detection and successful prosecution of drivers impaired by prescription medication or illegal drugs can therefore be difficult. Similarly, although urinalysis toxicology screens can detect the presence of such substances in the driver's bloodstream, these analyses are unable to demonstrate that the substance was actually causing impairment at the time of driving. In response to these problems, several jurisdictions are currently considering legislation that would establish "zero tolerance" laws for those drivers arrested for DUI and found to have drugs or medication in their system. Additionally, breathalyzers have been developed for the purpose of administering roadside or laboratory tests that can detect the actual level of a controlled substance in an individual's body.
Many jurisdictions require more serious penalties (such as jail time, larger fines, longer DUI program, the installation of ignition interlock devices) in cases where the driver's BAC is over 0.20, or 0.15 in some places. These additional sanctions are an attempt to deter and punish the operation of a vehicle at extremely high BAC levels and the concomitant danger posed to the safety of persons and property by heavily impaired drivers. In many cases, the reason given for these additional sanctions is because an average person would have passed out from that much alcohol. To be able to drive at that level, a person has to have consumed alcohol regularly for months in order to increase his/her alcohol tolerance and therefore is likely to have driven drunk repeatedly. However, since there is currently no standard test to measure alcohol tolerance, proponents of additional penalties for high-BAC offenders point to some studies that indicate that high-BAC offenders are more likely to be involved in a crash and more likely to recidivate. Critics of such laws point out that due to wide variations of alcohol tolerance, people with high tolerances will suffer the additional penalties, despite being less impaired than those with lower tolerances who drive with much lower BACs.
Some U.S. states also increase the penalties for drunk driving (even to the point of making it a felony) if certain other aggravating circumstances besides a high BAC are present, such as if the drunk driver caused an accident requiring the hospitalization of another person lasting greater than a specified period of time (often 72 hours ), in cases where an accident resulted in property damage exceeding a certain amount (often $500 ), or where the driver has prior (and relatively recent) convictions for drunk driving. In addition, most states observe administrative laws that further penalize people convicted of DUI, typically enforced by the department that issues driver's licenses, usually titled Department of Motor Vehicles (DMV), or Department of Licensing. Australia and the UK have higher alcohol consumption rates, lower ages for alcohol consumption, much lower sentencing regimes for DUI Manslaughter, and much lower incidences of DUI.
Similar laws apply to other activities involving transportation; Michigan prohibits intoxicated bicycling, horseback riding, buggy driving, use of motorized farm implements, or boating, the latter whether a pilot or passenger, with much the same threshold of intoxication.
Since 2004, Ohio has issued special license plates to all DUI offenders who are granted limited driving privileges such as work-related driving until a court can rule that they can have full privileges back. Unlike Ohio's standard-issue plates (which as of 2008 are red and blue on white), the DUI plates are yellow with red writing with no registration stickers or graphics.
In the US, most of the laws and penalties were greatly enhanced starting in the late 1970s, and through the 1990s, largely due to pressure from groups like Mothers Against Drunk Driving (MADD) and Students Against Driving Drunk (SADD) and leaders like Candy Lightner. Most significantly:
1. The legal presumption of intoxication from blood alcohol concentration was reduced to 0.10; more recently, and with federal pressure, all states have further reduced the limit to 0.08%.
2. A second drunk driving offense was created and eventually adopted in all states: driving with a BAC of 0.08% or higher; this was typically charged in addition to the traditional offense of driving under the influence.
3. Zero tolerance laws were enacted which criminalized driving a vehicle with 0.01 or 0.02 BAC for drivers under 21.
4. Automatic license suspension laws were universally adopted which provided for the immediate confiscation and administrative suspension of the driver's license if the BAC was 0.08% or if the driver refused testing.
MADD and other organizations are also widely cited for getting the drinking age raised to 21 in those states where it had once been lower. Also during this era, enforcement of drunk driving laws became a priority for police for the first time, and constitutional impediments to such practices as sobriety checkpoints were removed.
The USA has one of the worst DUI driving accident rates in the developed world while having lower to mid-range rates of alcohol consumption.
The following list of DUI symptoms, from a publication issued by the National Highway Traffic Safety Administration (DOT HS-805-711), is widely used in training officers to detect drunk drivers. After each symptom is a percentage figure which, according to NHTSA, indicates the statistical chances through research, that a driver is over the legal limit.
| Turning with wide radius | 65 |
| Straddling center or lane marker | 65 |
| Appearing to be drunk | 60 |
| Almost striking object or vehicle | 60 |
| Weaving | 60 |
| Driving on other than designated roadway | 55 |
| Swerving | 55 |
| Slow speed (more than 10mph below limit) | 50 |
| Stopping (without cause) in traffic lane | 50 |
| Drifting | 50 |
| Following too closely | 45 |
| Tires on center or land marker | 45 |
| Braking erratically | 45 |
| Driving into opposing or crossing traffic | 45 |
| Signaling inconsistent with driving actions | 40 |
| Stopping inappropriately (other than in lane) | 35 |
| Turning abruptly or illegally | 35 |
| Accelerating or decelerating rapidly | 30 |
| Headlights off | 30 |
If the officer observes enough to have a reasonable suspicion to legally justify a further detention and investigation, he will ask the driver to step out of the vehicle.
If the officer observes enough to have a reasonable suspicion to legally justify a further detention and investigation, he will ask the driver to step out of the vehicle. In some states (Texas and Louisiana, for example), if the officer has reasonable suspicion or probable cause to make the stop, the driver can be ordered out of the vehicle at any time, not just during a DUI investigation.
A sober person should be able to smoothly track the object with their eyes. In an intoxicated individual the eyes will jerk as they follow the object.
Although most law enforcement agencies continue to use a variety of these FSTs, increasingly a 3-test battery of standardized field sobriety tests (SFSTs) is being adopted. These tests are recommended by the National Highway Traffic Safety Administration (NHTSA) after studies indicated other FSTs were relatively unreliable. The NHTSA-approved battery of tests consists of the horizontal gaze nystagmus test, the walk-and-turn test, and the one-leg-stand. In some states, such as Ohio, only the standardized tests will be admitted into evidence, provided they were administered and objectively scored "in substantial compliance" with NHTSA standards (ORC 4511.19(D)(4)(b)). 
FSTs are more effective at determining the level of impairment than they are at estimating the driver's blood alcohol concentration (BAC). However, studies question whether the tests increase the officer's ability to judge either. In 1991, Dr. Spurgeon Cole of Clemson University conducted a study on the accuracy of FSTs. His staff videotaped individuals performing six common field sobriety tests, then showed the tapes to 14 police officers and asked them to decide whether the suspects had "had too much to drink and drive". The blood-alcohol concentration of each of the 21 DUI subjects was .00, unknown to the officers. The result: the officers gave their opinion that 46% of these innocent people were too drunk to be able drive. This study showed the possible inaccuracy of FSTs. Cole and Nowaczyk, "Field Sobriety Tests: Are they Designed for Failure?", 79 Perceptual and Motor Skills Journal 99 (1994).
An increasingly used field sobriety test involves having the suspect breathe into a small, handheld breath testing device. Called variously a PAS ("preliminary alcohol screening") or PBT ("preliminary breath test"), the units are small, inexpensive versions of their larger, more sophisticated instruments at the police stations, the EBTs ("evidentiary breath test"). Whereas the EBTs usually employ infrared spectroscopy, the PAS units use a relatively simple electrochemical (fuel cell) technology. Their purpose, along with other FSTs, is to assist the officer in determining probable cause for arrest. Although because of their relative inaccuracy they were never intended to be used in court for proving actual blood-alcohol concentration, some courts have begun to admit them as evidence of BAC.
Laws relating to what exactly constitutes probable cause vary from state to state. In California it is a refutable presumption that a person with a BAC of .08 or higher is driving under the influence. However, section 23610(a)(2) of the California Vehicle Code states that driving with a BAC between .05 and .08 "shall not give rise to any presumption that the person was or was not under the influence of an alcoholic beverage.
If the arrestee refuses to submit to chemical testing, he will usually be booked for driving under the influence; there will be no evidence for filing the second charge of driving with .08% blood alcohol content. In some cases the arrestee may be charged with DUI even after passing a breathalyzer test if he or she refuses also to take subsequent urine or blood tests. However, the refusal will carry increased penalties on the driving under the influence charge (typically a longer license suspension and/or an increased jail sentence), and the act of refusing may be admissible in court as evidence of "consciousness of guilt". In an increasing number of jurisdictions, if the suspect refuses to take a chemical test the police in some states may restrain the individual and forcefully withdraw blood; This is particularly common in situations involving an accident with injury or death. In some jurisdictions this may require obtaining a warrant from a judge.
While chemical tests are used to determine the driver's BAC, they do not determine the driver's level of impairment. However, state laws usually provide for a rebuttable legal presumption of intoxication at blood alcohol levels of .08 or higher (see blood alcohol test assumptions). The accuracy of breath, blood and urine testing is a subject of some dispute, with various scientific studies indicating unreliable results (see breathalyzer). In any case, breath and urine tests can only estimate the BAC at the time the test is taken, which can be different than when the vehicle was actually operated. Evidence of the BAC at time of driving is often presented in the form of retrograde extrapolation, a questionable process whereby earlier blood alcohol levels are estimated by applying a formula developed in 1932 known as the Widmark factor.
Most of the time, the driver will either be kept in a holding cell (sometimes referred to as the "drunk tank") until he is deemed sober enough to be released on bail or on his "own recognizance" ("O.R."). A date to appear in court for an arraignment will be given to him. If he cannot make bail or is not granted O.R., he will be kept in jail to wait for the arraignment on remand.
These innovative courts use substance abuse intervention with hard-core repeat offenders who plead guilty to driving while intoxicated. Those accepted into the diversionary program are required to abstain from alcohol. Some are required to wear a device that monitors and records any levels of alcohol detected in their bloodstreams.
An SR-22 is an official documentation required in all 50 states, including the District of Columbia which proves minimum liability insurance coverage. It can be used to redeem a suspended drivers license and get a car registered at the local Department of Motor Vehicles (DMV). An SR-22 Filing is a form issued by an insurance company which removes a suspension order placed by the DMV's office on your driving privilege. The filing provides a guarantee to the state that an insurance company has issued at least minimum liability coverage for the person making that filing and that the insurance company will notify the DMV should the insurance ever lapse for any reason.