Here are some factors that can greatly affect the alcohol induced impairment:

1.Tolerance in Alcohol. Studies that suggested that the frequent performance of a particular act while under the influence (especially driving under the influence) of a certain chemical substance such as alcohol and drugs can make a person become less sensitive to the damage of a given blood alcohol concentration or mostly called as BAC. However, even though the impairment cause by alcohol may not be apparent during a particular routine task, its performance will only worse in unexpected or novel situations. In some DUI classes particularly in California DUI class, they have found out that some people were only able to conduct such act is because they have been greatly impaired by alcoholic beverages.

2.AGE and Gender. Based on the driven miles, the highest fatality rates among drivers are found to be evident among the oldest and youngest drivers. When it is being compared to the driver fatality rate for ages 25 to 65, the rate for the drivers with ages 16 to 19 is about four times higher and drivers who are over the age of 85 is nine times higher fatality rate. The reason why the fatality rate of car crash is higher for older people is because there are also factors which makes driving unsafe. Such factors include proper attention, vision problems, cognition and perception. Male drivers who are younger than 21 years old, there is a BAC increase of about 0.02% more than the doubles of the relative risk of a fatal crash for a single vehicle. Women who belong in this age group were found out to have lower risk than men in every aspect of BAC. Due to the lack of driving experiences, younger drivers have greater risk for a car crash.

3.Lack of Sleep. People who have enrolled in California DUI classes have stated that some of them are actually not drunk and they were just drowsy due to lack of sleep. Drowsiness makes the risk for car crash becomes higher and studies have shown that BACs which are as low as 0.01% makes susceptibility to sleepiness to increase.