Drinking and Driving
Impairment and blood alcohol concentration
In the first part of this section you learned about intoxication, which is identified by observing a person’s mental and physical state.
Like intoxication, impairment can be an observed state; however, it can also be measured. The law recognizes that impairment begins when a person has a blood alcohol concentration (BAC) at or exceeding 50 milligrams of alcohol per 100 millilitres of blood, or .05%. The criminal code fail level for impairment is when a person's BAC is at or above .08%. This appears to be a small amount — about one drop of alcohol in 1,200 drops of blood. However, the effects of even a fraction of 1% alcohol content in the bloodstream are potent. Consider that:
- a BAC of .30% can cause a person to lose consciousness.
- with a BAC of .40%, a person will be in a coma or could die.
A person can be legally unfit to drive if:
- his or her BAC is at or above .05% or
- his or her ability to drive is impaired by the use of alcohol, drugs or other factors.
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Many law enforcement agencies use breath alcohol testing devices like the Breathalyzer to determine a person’s BAC. In the absence of admissible evidence of BAC, the prosecution in a drunk-driving case may rely on the observations of a police officer or a layperson as to the accused person's impairment. Such evidence may include erratic driving and physical and behavioural indicators like slurred speech, bloodshot eyes and difficulty walking a straight line.
Thus, a person can be guilty of impaired driving even though their BAC is below .05%. Similarly, a person is guilty of impaired driving with a BAC at or above .05%, whether or not their ability to operate the vehicle is visibly affected by alcohol consumption.
Penalties for Impaired Driving
Any person who is found to be driving with a BAC at or above .05% can face penalties including immediate suspension of their driver's license, vehicle impoundment and monetary fines. Click here for more detail on BC's drinking and driving legislation.
The only way of accurately measuring BAC is to use a Breathalyzer or conduct a blood test. A customer's BAC will depend on factors including his or her sex, weight, the number of drinks he or she has consumed and the number of hours since the first drink (see chart on How to Calculate BAC).
A practical technique for you to estimate a customer's BAC is to observe how many standard drinks (defined as a drink containing the equivalent of 0.6 ounces of 100% alcohol) are served and consumed by the customer while at your premises.
The standard drink
A standard drink (SD) is a unit that is used to quantify alcohol intake. A standard drink varies from country to country. In Canada, a standard drink is any drink that contains 13.6 grams of pure alcohol or the equivalent of 0.6 ounces of 100% alcohol.
Different alcoholic beverages have different concentrations of alcohol. For example, most beers contain 5% alcohol; wines contain 12 to 13% alcohol; and spirits can contain 40% alcohol or more. In addition, different shapes and sizes of containers will contain different volume of alcoholic drinks.
One standard drink is approximately:
- One 12-ounce can of beer, containing 5% alcohol (12 x 0.05 = 0.60 = 1 SD)
- One 5-ounce glass of wine, containing 12% alcohol (5 x 0.12 = 0.60 = 1 SD)
- One and a half-ounce hard liquor or spirits, containing 40% alcohol (1.5 x 0.40 = 0.60 = 1 SD)
This means that a 12-ounce glass of beer with 5% alcohol, a 5-ounce glass of wine with 12% alcohol and a 1.5-ounce of spirits with 40% alcohol are all considered standard drinks. Note that each drink has different alcohol concentration and is available in different volumes. However, each of these is called a standard drink because it has the same effect on the human body as 0.6 ounces of 100% alcohol.
The size of a drink matters because the amount of alcohol in beverages can differ. Therefore, to calculate a standard drink, you need to know:
- The volume of alcoholic beverage
- The percentage (concentration) of alcohol in that beverage
Larger volumes or higher concentrations will increase the number of standard drinks consumed; smaller volumes or lower concentrations will decrease the number of standard drinks consumed.
Depending on what type of drink your patrons are drinking, they may be drinking less than or more than a standard drink. For example, with the introduction of low-alcohol beer and wine, a normal serving will be less than a standard drink, because the beverage has lower alcohol content. A five-ounce glass of 12% alcohol wine is equal to one SD (12 x 0.05 = 0.60 = 1 SD). Therefore, a glass of light wine at 9% alcohol volume would be less than one SD (5 x 0.9 = 0.45 which is less than 1 SD). Similarly, light beers generally contain 4% alcohol, which is less than one SD.
There are also higher alcohol versions of beer and wine. Malt beer and ciders often contain 7% alcohol. Some full-bodied red and fortified wines can range from 14.5% to 21% alcohol levels. These higher alcohol versions should be served at a slower rate, as they are more potent.
Spirits in mixed drinks can be sold in 1, 1¼ or 1½-ounce shots. Again, the alcohol volume will affect the standard drink calculation.
It is important to understand the standard drink and its equivalencies because it allows you to monitor your patrons' intake. The liver can only process a fixed amount of alcohol, about one standard drink per hour. By determining the number of standard drinks consumed by a customer over time, and consulting the chart on How to Calculate BAC (see Appendix D), you will be able to monitor the consumption of your customers to help ensure that they do not leave your premises and drive while impaired.
Calculating the standard drink
The following is a basic SD comparison. All of these drinks have the same effect on the body and are equivalent to one SD.
|12 ounces beer with 5% alcohol volume = 12 x 0.05 = 0.6 ounces alcohol = 1 SD||1 ½ ounces spirits with 40% alcohol volume = 1.5 x 0.40 = 0.6 ounces alcohol = 1 SD||5 ounces wine with 12% alcohol volume = 5 x 0.12 = 0.6 ounces alcohol = 1 SD|
How to use this knowledge on the job
The key to responsible alcohol service is to know when to discontinue service. Knowing how many standard drinks have been consumed by your patrons can help you slow down service and ensure responsible beverage service.
Assess guests as they enter your establishment. Are they already showing signs of intoxication? What factors (like their gender, weight, or age) might affect their impairment level? Try to determine ahead of time approximately how many drinks to serve to individual customers before discontinuing service.