Alcohol and Drugs
Alcohol and drugs is the twelfth domain of the Louisiana CDL General Knowledge exam. It tests the legal limits for commercial drivers, the effects of alcohol and drugs on driving, and the consequences of refusing a test or driving impaired.
Legal limits
In Louisiana, a CDL holder is over the limit at a blood alcohol concentration of 0.04 or higher while operating a commercial motor vehicle; the non-commercial limit is 0.08. Controlled substances are prohibited regardless of state law, and a refusal to submit to testing carries serious consequences.
Effects
Alcohol slows reaction time, impairs judgment and vision, and reduces coordination. Prescription and over-the-counter drugs can also impair driving; ask a pharmacist or doctor about effects. Combining alcohol with drugs increases impairment.
Reporting and responsibility
A CDL holder must notify the employer of certain convictions and cannot hide a suspension. Alcohol does not “burn off” with coffee, a cold shower, or exercise; time is the only thing that lowers BAC.
Worked example
A driver with a 0.04 BAC in a commercial vehicle is stopped at a checkpoint. The driver is over the CDL limit even though the reading would be legal for a non-commercial driver in Louisiana. The reasoning: the commercial standard is stricter because of the vehicle's size and consequences of a crash.
Traps
Believing one drink is always safe, thinking coffee sobers you up, and assuming a prescription drug is safe because it is legal are common errors.