No truck driver can have any illegal drugs in his system at any time.  The United States Congress recognized the need for drug and alcohol free semi-truck industry, because of how dangerous these driver are to everyone on the road.

The rule comes under the regulation defined in 49 CFR Part 40.  For short, lawyers and industry insiders will call the rule Part 40.  Part 40 applies to all DOT registered testing, regardless of the type of transportation.  This means in addition to Part 40 applying to semi-truck drivers, it also applies to airline pilots and other industries.

Since 1990, the FMCSR have made drug testing a mandatory part of a driver’s qualification for his license to drive a commercial driver’s license (CDL).   The regulations test for both drugs and alcohol, and allow for regular random drug testing. In addition to random drug testing, there are drug tests when there is an accident that must occur shortly after the accident.


Semi-truck drivers cannot drink nor have any alcohol in their system when they are operating a commercial motor  vehicle.  This is a zero tolerance policy.  Any blood alcohol content in a driver’s blood will be enough for a fine, and possibly worse.  If there is alcohol in the blood at the time of an accident, often the truck driver will be presumed to be negligent (at fault) for at least part of the semi-truck accident.

The alcohol rule is a federal rule (meaning it applies to every state in the United States) and is defined in rule 49 CFR Part 40.  This rule is generally spoken of as Rule 40, by those in the industry.

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