As a driver under the age of 21, you have a higher risk of being involved in a car accident, whether under the influence of alcohol or not. Therefore, the law tries to limit these occurrences as much as possible by enforcing stricter rules for drivers under the age of 21.
Drivers over the age of 21 can only legally drive when their blood alcohol concentration (BAC) is below .08 percent. This is because studies show that actions become impaired once a person has a higher amount in their blood stream. If you are under the age of 21, you must have practically no alcohol in your system, and measure a BAC of .02 percent or less.
Why is there a no tolerance approach for those under the age of 21?
There are two main reasons why there is a zero tolerance law on underage drinking and driving. The first is because it is illegal for anyone under the age of 21 to drink alcohol in general, apart from certain limited exceptions.
In addition to this, it is a more serious offense to be driving with some alcohol in your system, because as a young person, you have a limited driving experience and are more likely to engage in risky behavior, and therefore, having a higher chance of causing an accident.
What if the results are not accurate?
The instruments used to measure BAC, Breathalyzers, are not always accurate, and they can often make a mistake at determining such low quantities of alcohol. Therefore, it is important to contest your result if you have been accused of an underage DUI.
Source: Underage drinking facts, “Underage Blood Alcohol Content,” accessed March 01, 2018