Blood Alcohol Level
Drink and drive offenses can be monitored by using Blood Alcohol Level (BAL) and many countries use either BAL or a breath analyzer.
Blood alcohol level (BAL) or Blood alcohol content (BAC) is the amount of alcohol in your blood stream.
It is calculated in milligrams of alcohol per hundred millilitres of blood or milligram percent. In some countries it is reported as grams of alcohol per litre (thousand millilitre) (Litre).
By using the number of drinks consumed and the time over it was consumed; one can calculates safe limits of alcohol consumption (See medindia BAC calculators link). However it is not a good measure of intoxication as there is a large variation in physiology and individual alcohol tolerance.