Drunk driving
Drunk driving is the act of driving under the influence of alcohol. A small increase in the blood alcohol content increases the relative risk of a motor vehicle crash.
In the United States, alcohol is involved in 32% of all traffic fatalities.
Terminology
United States
In the United States, most states have generalized their criminal offense statutes to driving under the influence. These DUI statutes generally cover intoxication by any drug, including alcohol. Such laws may also apply to operating boats, aircraft, farm machinery, horse-drawn carriages, and bicycles. Specific terms used to describe alcohol-related driving offenses include "drinking and driving", "drunk driving", and "drunken driving". Most DUI offenses are alcohol-related so the terms are used interchangeably in common language, and "drug-related DUI" is used to distinguish.United Kingdom
In the United Kingdom, there are two separate offences to do with alcohol and driving. The first is "Driving or attempting to drive with excess alcohol", the other is known as "In charge of a vehicle with excess alcohol" or "drunk in charge" due to the wording of the Licensing Act 1872. In relation to motor vehicles, the Road Safety Act 1967 created a narrower offense of driving a vehicle while having breath, blood, or urine alcohol levels above the prescribed limits. These provisions were re-enacted in the Road Traffic Act 1988. A separate offense in the 1988 Act applies to bicycles. While the 1872 Act is mostly superseded, the offense of being "drunk while in charge... of any carriage, horse, cattle, or steam engine" is still in force; "carriage" has sometimes been interpreted as including mobility scooters.European Union
In the European Union, the term "drink-driving" is used in the Directive 2015/413 of the European Parliament and of the Council of 11 March 2015 facilitating cross-border exchange of information on road-safety-related traffic offences. In this directive drink-driving means driving while impaired by alcohol, as defined in the law of the Member State of the offence.Measurement of intoxication
Depending on the jurisdiction, a drunk driver's level of intoxication may be measured by police using three methods: blood, breath, or urine, resulting in a blood alcohol concentration, breath alcohol concentration, or urine result. For law enforcement purposes, breath analysis using a breathalyzer is the preferred method, since results are available almost instantaneously. A measurement in excess of the specific threshold level, such as a BAC of 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%, 0.15%, or 0.25%. In many jurisdictions, police officers can conduct field tests of suspects to look for signs of intoxication. There have been cases in Canada where officers have come upon a suspect who is unconscious after a crash and officers have taken a blood sample.
With the advent of a scientific test for BAC, law enforcement regimes moved from field sobriety testing to having more than a prescribed amount of blood alcohol content while driving. However, this does not preclude the simultaneous existence and use of the older subjective tests in which police officers measure the intoxication of the suspect by asking them to do certain activities or by examining their eyes and responses. The validity of the testing equipment/methods for determining breath and blood alcohol and mathematical relationships between breath/blood alcohol and intoxication levels have been criticized. Improper testing and equipment calibration is often used in defense of a DUI or DWI.
Effects of alcohol
Effects on cognitive processes
Alcohol is a depressant, which mainly affects the function of the brain. Alcohol first affects the most vital components of the brain and "when the brain cortex is released from its functions of integrating and control, processes related to judgment and behavior occur in a disorganized fashion and the proper operation of behavioral tasks becomes disrupted." Alcohol weakens a variety of skills that are necessary to perform everyday tasks. Drinking enough alcohol to cause a blood alcohol concentration of 0.03–0.12% typically causes a flushed, red appearance in the face and impaired judgment and fine muscle coordination. A BAC of 0.09% to 0.25% causes lethargy, sedation, balance problems, and blurred vision. A BAC from 0.18% to 0.30% causes profound confusion, impaired speech, staggering, dizziness, and vomiting. A BAC from 0.25% to 0.40% causes stupor, unconsciousness, anterograde amnesia, vomiting, and respiratory depression. A BAC from 0.35% to 0.80% causes a coma, life-threatening respiratory depression, and possibly fatal alcohol poisoning. There are a number of factors that affect the time in which BAC will reach or exceed 0.08, including weight, the time since one's recent drinking, and whether and what one ate within the time of drinking. A 170lb male can drink more than a 135lb female, before being over the BAC level.One of the main effects of alcohol is severely impairing a person's ability to shift attention from one thing to another, "without significantly impairing sensory motor functions." This indicates that people who are intoxicated are not able to properly shift their attention without affecting the senses. People that are intoxicated also have a much more narrow area of usable vision than people who are sober. The information the brain receives from the eyes "becomes disrupted if eyes must be turned to the side to detect stimuli, or if eyes must be moved quickly from one point to another."
Effects on driving
Research shows an exponential increase of the relative risk for a crash with a linear increase of BAC. NHTSA reports that the following blood alcohol levels in a driver will have the following predictable effects on his or her ability to drive safely: A BAC of.02 will result in a "ecline in visual functions, a decline in the ability to perform two tasks at the same time "; A BAC of.05 will result in "educed coordination, reduced ability to track moving objects, difficulty steering, reduced response to emergency driving situations"; A BAC of.08 will result in "oncentration, short-term memory loss, speed control, reduced information processing capability, impaired perception"; A BAC of.10 will result in "educed ability to maintain lane position and brake appropriately"; and A BAC of.15 will result in "ubstantial impairment in vehicle control, attention to driving task, and in necessary visual and auditory information processing."Several testing mechanisms are used to gauge a person's ability to drive, which indicate levels of intoxication. One of these is referred to as a tracking task, testing hand–eye coordination, in which "the task is to keep an object on a prescribed path by controlling its position through turning a steering wheel. Impairment of performance is seen at BACs of as little as 0.7 mg/mL." Another form of tests is a choice reaction task, which deals more primarily with cognitive function. In this form of testing both hearing and vision are tested and drivers must give a "response according to rules that necessitate mental processing before giving the answer." This is a useful gauge because in an actual driving situation drivers must divide their attention "between a tracking task and surveillance of the environment." It has been found that even "very low BACs are sufficient to produce significant impairment of performance" in this area of thought process.
Grand Rapids Dip
A 1964 paper by Robert Frank Borkenstein studied data from Grand Rapids, Michigan. The main finding of the Grand Rapids study was that for higher values of BAC, the collision risk increases steeply; for a BAC of 0.15%, the risk is 25 times higher than for zero blood alcohol. The BAC limits in Germany and many other countries were set based on this Grand Rapids study. Subsequent research showed that all extra collisions 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%. One surprising aspect of the study was that, in the main analysis, a BAC of 0.01–0.04% was associated with a lower risk of collisions than a BAC of 0%, a feature referred to as the Grand Rapids Effect or Grand Rapids Dip. A 1995 Würzburg University study of German data similarly found that the risk of collisions appeared to be lower for drivers with a BAC of 0.04% or less than for drivers with a BAC of 0%.Studies of alcohol impairment on tests of driving ability have found that impairment starts as soon as alcohol is detectable. Thus, the literature has for the most part treated the Grand Rapids Dip as a statistical effect, similar to Simpson's paradox. The analysis in the Grand Rapids paper relied primarily on univariate statistics, which could not isolate the effects of age, gender, and drinking practices from the effects of other variables. In particular, when the data is re-analyzed by constructing separate BAC-crash rate graphs for each drinking frequency, there are no J-shapes in any of the graphs and collision rates increase starting from 0% BAC. The analysis of the Grand Rapids study was biased by including drivers younger than 25 and older than 55 that did not drink often but had significantly higher crash rates even when not drinking alcohol. A newer study using data from 1997-1999 replicated the Grand Rapids dip but found that adjusting for covariates using logistic regression made the dip disappear.
Perceived recovery rate
A direct effect of alcohol on a person's brain is an overestimation of how quickly their body is recovering from the effects of alcohol. A study, discussed in the article "Why drunk drivers may get behind the wheel", was done with college students in which the students were tested with "a hidden maze learning task as their BAC both rose and fell over an 8-hour period." The researchers found through the study that as the students became more drunk there was an increase in their mistakes "and the recovery of the underlying cognitive impairments that lead to these errors is slower, and more closely tied to the actual blood alcohol concentration, than the more rapid reduction in participants' subjective feeling of drunkenness."The participants believed that they were recovering from the adverse effects of alcohol much more quickly than they actually were. This feeling of perceived recovery is a plausible explanation of why so many people feel that they are able to safely operate a motor vehicle when they are not yet fully recovered from the alcohol they have consumed, indicating that the recovery rates do not coincide.
This thought process and brain function that is lost under the influence of alcohol is a very key element in regards to being able to drive safely, including "making judgments in terms of traveling through intersections or changing lanes when driving." These essential driving skills are lost while a person is under the influence of alcohol.