Driving under the influence
Driving under the influence (DUI), driving while intoxicated (DWI), drunken driving, drunk driving, operating under the influence, drinking and driving, or impaired driving is the crime of driving a motor vehicle while impaired by alcohol or other drugs including those prescribed by physicians.
In the case of alcohol, a drunk driver's level of intoxication is typically determined by a measurement of blood alcohol content or BAC. A BAC measurement in excess of a specific threshold level, such as 0.05% or 0.08%, defines the criminal offense with no need to prove impairment. In some jurisdictions, there is an aggravated category of the offense at a higher BAC level, such as 0.12%. In most countries, anyone who is convicted of injuring or killing someone while under the influence of alcohol or other drugs can be heavily fined in addition to being given a lengthy prison sentence. In the United States, DUI and alcohol-related crashes produce an estimated $45 billion in damages every year.
In some U.S. and German studies BAC level 0.01-0.03% predicted a lower crash risk than BAC 0%, possibly due to extra caution, whereas BACs 0.08% or higher seem to be responsible for almost all extra accidents caused by alcohol. For a BAC of 0.15% the risk is 25-fold.
Legal definitions of the offense
The criminal offense may not involve actual driving of the vehicle, but rather may broadly include being physically in control of a car while intoxicated even if the person charged is not driving.
Blood alcohol content (BAC)
With the advent of a scientific test for blood alcohol content (BAC), enforcement regimes moved to pinning culpability for the offense to strict liability based on driving while having more than a prescribed amount of blood alcohol, although this does not preclude the simultaneous existence of the older subjective tests. BAC is most conveniently measured as a simple percent of alcohol in the blood by weight. Research shows an exponential increase of the relative risk for a crash with a linear increase of BAC as shown in the illustration. BAC does not depend on any units of measurement. In Europe it is usually expressed as milligrams of alcohol per 100 milliliters of blood. However, 100 milliliters of blood weighs essentially the same as 100 milliliters of water, which weighs precisely 100 grams. Thus, for all practical purposes, this is the same as the simple dimensionless BAC measured as a percent. The per mille (promille) measurement, which is equal to ten times the percentage value, is used in Denmark, Germany, Finland, Norway and Sweden.
The validity of the testing equipment/methods and mathematical relationships for the measurement of breath and blood alcohol have been criticized.
Driving while consuming alcohol may be illegal within a jurisdiction. In some it is illegal for an open container of an alcoholic beverage to be in the passenger compartment of a motor vehicle or in some specific area of that compartment. There have been cases of drivers being convicted of a DUI when they were not observed driving after being proven in court they had been driving while under the influence.
In the case of an accident, insurance may be automatically declared invalid, i.e. the drunk driver is fully responsible for damages. Within the American system, citation for driving under the influence also causes a major spike in car insurance premiums[clarification needed]—94.1% in the first year, and still 63.5% higher by the third year.
The German model serves to reduce the number of accidents by identifying unfit drivers and removing them from until their fitness to drive has been established again. The Medical Psychological Assessment (MPA) works for a prognosis of the fitness for drive in future, has an interdisciplinary basic approach and offers the chance of individual rehabilitation to the offender.
George Smith, a London Taxi cab driver, ended up being the first person to be convicted of driving while intoxicated, on September 10, 1897. He was fined 25 shillings, which is equivalent to £124 in 2014.
BAC and risks
Studies show that a high BAC increases the risk of accidents whereas it is not clear of a BAC of 0.01%-0.05% slightly increases or decreases the risk. One study suggests that already a BAC of 0.04-0.05% would slightly increase the risk whereas some studies suggest that a BAC of 0.01-0.04% would slightly lower the risk, possibly due to the drivers being more cautious.
Both the influential study by Borkenstein et al. and the empirical German data on the 1990s demonstrated that the risk of accident is lower or the same for drivers with a BAC of 0.04% or less than for drivers with a BAC of 0%. For a BAC of 0.15% the risk is 25-fold. The 0.08% BAC limit in Germany and the limits in many other countries were set based on the study by Borkenstein et al. 
Wuerzburg University researchers showed that all extra accidents caused by alcohol were due to at least 0.06% BAC, 96% of them due to BAC above 0.08%, and 79% due to BAC above 0,12%. In their study based on the 1990s German data, the effect of alcohol was higher for almost all BAC levels than in Borkenstein et al. 
In the Blomberg et al. study the crash statistics indicated a lowered risk for BACs 0.01% to 0.04% (87-92% of the risk of a sober driver). When adjusted for the demographic variables, already at 0.05% BAC the risk seemed to be slightly higher than for the same drivers in 0% although less than for average 0% drivers. After this adjustment, the lower risk at BAC 0.01-0.03% (92%-94%) was not significant. When also the estimated selection bias was corrected, the risk for these drivers was estimated to be 3-6% higher than for sober drivers, although the difference was not significant. In Alsop's Grand Rapids study the accident risk at BAC 0.01-0.03% was just 80-96% of that of sober drivers. 
Also in the Grand Rapids study by Alsop, 0.01-0.03% BAC lead to a mere 80%-96% crash risk, possibly due to extra caution. 
Field sobriety testing
To attempt to determine whether a suspect is intoxicated, police officers may sometimes conduct what is known as a "field sobriety test".
A police officer in the United States must have probable cause to make an arrest for driving under the influence. In establishing probable cause for a DUI arrest officers frequently consider the suspect's performance of Standardized Field Sobriety Tests. The US National Highway Traffic Safety Administration (NHTSA) has established a standard battery of three roadside tests that are recommended to be administered in a standardized manner in making this arrest decision. The first test typically administered is the Horizontal Gaze Nystagmus test. When this test is conducted the officer is looking for the involuntary jerking of the suspect's eyes. The second test administered is the Walk and Turn (WAT) test. This test is a divided attention test and also measures balance. It requires the suspect to walk heel-to-toe on a line along with other instructions. The final test is the One Leg Stand (OLS). The OLS test requires the suspect to stand on one leg for 30 seconds and also measures balance, coordination, and similar to the WAT test, divides the suspect's attention.
Drunk driving law by country
Many employers or occupations have their own rules and BAC limits; for example, the United States Federal Railroad Administration has a 0.04% limit for train crew. Certain large corporations have their own rules; for example, Union Pacific Railroad has their own BAC limit of 0.02% that, if violated during a random test or a for-cause test—for example, after a traffic accident—can result in termination of employment with no chance of future re-hire. Some jurisdictions have multiple levels of BAC for different categories of drivers; for example, the state of California has a general 0.08% BAC limit, a lower limit of 0.04% for commercial operators, and a limit of 0.01% for drivers who are under 21 or on probation for previous DUI offenses.
Many states in the U.S. and the Federal government of Canada have adopted truth in sentencing laws that enforce strict guidelines on sentencing, differing from previous practice where prison time was reduced or suspended after sentencing had been issued. Some jurisdictions have judicial guidelines requiring a mandatory minimum sentence. DUI convictions can result in multi-year jail terms and other penalties ranging from expensive fees to forfeiture of one's license plates and vehicle. Some jurisdictions require that drivers convicted of DUI offenses use special license plates that are easily distinguishable from regular plates. These plates are known in popular parlance as "party plates" or "whiskey plates".
The specific criminal offense may be called, depending on the jurisdiction, driving under the influence [of alcohol or other drugs] (DUI), driving under the influence of intoxicants (DUII), driving while intoxicated (DWI), "operating vehicle under the influence of alcohol or other drugs" (OVI), operating under the influence (OUI) operating while intoxicated (OWI), operating a motor vehicle while intoxicated (OMVI), driving under the combined influence of alcohol and/or other drugs, driving under the influence per se or drunk in charge [of a vehicle]. Many such laws apply also to motorcycling, boating, piloting aircraft, use of motile farm equipment such as tractors and combines, riding horses or driving a horse-drawn vehicle, or bicycling, possibly with different BAC level than driving. In some jurisdictions there are separate charges depending on the vehicle used, such as BWI (bicycling while intoxicated), which may carry a lighter sentence.
In the United States, local law enforcement agencies made 1,467,300 arrests nationwide for driving under the influence of alcohol in 1996, compared to 1.9 million such arrests during the peak year in 1983. In 1997 an estimated 513,200 DWI offenders were in prison or jail, down from 593,000 in 1990 and up from 270,100 in 1986.
Drunk in charge
In British law it is a criminal offence to be drunk in charge of a motor vehicle. The definition depends on such things being in or near the vehicle, and having access to a means of starting the vehicle's engine and driving it away.
Health care, working, and prescription drugs
If a worker who drives has a health condition which can be treated with opioids, then that person's doctor should be told that driving is a part of the worker's duties and the employer should be told that the worker could be treated with opioids. Workers should not use impairing substances while driving or operating heavy machinery like forklift trucks or cranes. If the worker is to drive, then the health care provider should not give them opioids. If the worker is to take opioids, then their employer should assign them work which is appropriate for their impaired state and not encourage them to use safety sensitive equipment.
- DR10, UK police code
- Driving license
- Drug–impaired driving
- Drunk drivers
- Drunk walking
- DWI court
- Ignition interlock device
- Mothers Against Drunk Driving (MADD)
- National Motorists Association
- Remove Intoxicated Drivers
- Sobriety checkpoints
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