When Are Commercial Truck Drivers Required to Be Tested?

The U.S. Department of Transportation (DOT) drug and alcohol testing regulations for Commercial Driver License (CDL) employees requires that screenings be completed at certain times and reasons. The regulations require 5-panel testing for substances including: marijuana, cocaine, Opiates (opium and codeine derivatives), amphetamines and methamphetamines, and  Phencyclidine or PCP. 


While drug tests can be completed randomly or when there is suspicion of use, there are also some key times during employment as a commercial driver that employers. supervisors, or substance abuse professionals could request a test. Here is a quick overview of the times when a CDL may be required to complete and pass a drug screening test or an alcohol use test. 


Before an employer can permit a CDL to operate a CMV (commercial motor vehicle such as a truck or bus) on a public road, new drivers must be tested and receive a negative test result. Alcohol testing may also be required, but only if it is required of all CDL drivers. According to the regulations, if a driver is removed from a random testing pool for more than 30 days, the driver must again be pre-employment tested.

Post Accident

In the case when a driver is involved in a fatal crash, an accident that has led to injury, or has received a traffic citation after an incident, there will be both drug and alcohol testing. The alcohol test must occur within 8 hours, and the drug test must occur within 32 hours. 

Reasonable Suspicion

In the case when a commercially licensed driver is exhibiting signs or drug or alcohol use or abuse, a DOT-trained supervisor can direct a driver to be drug or alcohol tested. This decision must be made based upon observations, behaviors, speech, appearance, and (potentially) smell. It is not something that is done randomly, but rather with evidence of concern. 

Random Testing 

In addition to testing at the start of employment, after an accident, and when there is reasonable suspicion, CDL drivers may also be required to take part in random testing. 


This testing is unannounced. Alcohol testing may only be conducted when the driver is on-duty, but random drug testing could occur even during off-duty times. Once a driver is given notification that they have been chosen for random testing, they must report to a testing location immediately. A delayed arrival will be tantamount to a positive test. 

Return-to-Duty Testing 

Return-to-duty tests require “direct observation” as prescribed in 49 CFR 40.67. They are only required after an employee has completed the “return-to-duty” process, before returning to perform a safety sensitive function. 

Follow-Up Testing 

Drug and alcohol tests that fall into the “Follow Up” category are usually required as prescribed by the substance abuse professional (SAP) who signs the return-to-duty report.  This usually consists of a minimum of at least six unannounced directly observed tests conducted during the first 12 months following the return-to-duty test. The SAP can prescribe followup testing for a maximum of 5 years for drivers who have tested “positive” or “refused to test.” 

These six categories are the required protocol set forth by the Department of Transportation regulations as they apply to CDL drivers. To find out more about the type of testing you are being asked for consult the Clearinghouse Navigator’s “Frequently Asked Questions.”