Driving under the influence

Driving under the influence (DUI), driving while intoxicated (DWI), drunken driving, drunk driving, drink driving,  operating under the influence, drinking and driving, or impaired driving is the act of driving a motor vehicle with blood levels of alcohol in excess of a legal limit ("Blood Alcohol Content", or "BAC"). Similar regulations cover driving or operating certain types of machinery while affected by drinking alcohol or taking other drugs, including, but not limited to prescription drugs. This is a criminal offense in most nations. Convictions do not necessarily involve actual driving of the vehicle.

In most jurisdictions a measurement such as a blood alcohol content (BAC) in excess of a specific threshold level, such as 0.05% or 0.08% defines the offense, with no need to prove impairment or being under the influence of alcohol. In some jurisdictions, there is an aggravated category of the offense at a higher level e.g. 0.12%. In most countries, anyone who is convicted of injuring or killing someone while under the influence of alcohol or drugs can be heavily fined, as in France, in addition to being given a lengthy prison sentence. Some jobs have their own rules and BAC limits, for example commercial pilot, and the Federal Railroad Administration in the United States has a 0.04% limit for train crew. Some jurisdictions have multiple levels of BAC; for example, the state of California has a 0.08% BAC limit, which is lowered to 0.04% if the operator holds a commercial driver's license. The California BAC limit is 0.01% for those younger than 21 years of age and those on probation for a previous DUI conviction. Some large corporations have their own rules; 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.

Many states in the U.S. and provinces in 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. Penalties for DUI charges range from expensive fees to forfetiruree of your license plates and in some serious circumstances, your vehicle.

The specific criminal offense may be called, depending on the jurisdiction, driving under the influence [of alcohol or other drugs] (DUI), driving under intense influence (DUII), driving while intoxicated (DWI), 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.

Blood alcohol level (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 Norway, Sweden and Finland.

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. Drivers have been convicted even when they were not observed driving if it could be safely concluded they had been driving while intoxicated.

Within the American system, citation for driving under the influence also causes a major spike in car insurance premiums – 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 who use to be a London Taxi cab driver, ended up the first person to be convicted of driving while intoxicated, on September 10, 1897. He had been fined 25 shillings, which is equivalent to £71.33 in 2005 pounds.

Field sobriety testing
Historically, guilt was established by observed driving symptoms, such as weaving; administering field sobriety tests, such as a walking a straight line heel-to-toe or standing on one leg for 30 seconds; and the arresting officer's subjective opinion of impairment. The officer must correctly perform the Field Sobriety Tests (FSTs) that are approved by the National Highway Transportation Safety Administration (NHTSA). The US Department of Transportation explains the Field Sobriety Test as, "a battery of three tests administered and evaluated in a standardized manner to obtain validated indicators of impairment and establish probable cause for arrest." Starting with the introduction in Norway in 1936 of the world’s first per se law which made it an offense to drive with more than a specified amount of alcohol in the body, objective chemical tests have gradually supplanted the earlier purely judgmental ones. Limits for chemical tests are specific for blood alcohol concentration or concentration of alcohol in breath.

Drunk driving law by country
The laws relating to drunk driving vary between countries and varying blood alcohol content is allowed before a conviction is made.