This sounds a little far reaching, but could this be true ? Not mentioned is the alcohol issue and driving impaired which I know happens on a regular basis. There is the full video of the hearing in this link.

Group tells Congress thousands of truckers are ‘illicit drug users’ & recommends 300,000 driver purge
During a major meeting between trucking industry stakeholders and Congress today, a group comprised of multiple mega-carriers told lawmakers that they have evidence that thousands of truck drivers are “manipulating” drug testing protocols and should be removed from the nation’s highways.
On Wednesday, June 12, numerous trucking industry groups met with the U.S. House of Representatives Committee on Transportation and Infrastructure for a hearing called “Under Pressure: The State of Trucking in America.” Groups like the American Trucking Associations (ATA) and the Owner-Operator Independent Drivers Association (OOIDA) were in attendance at the hearing.
One of these groups, the Alliance for Driver Safety & Security (more commonly known as the Trucking Alliance) told lawmakers that they believe that “thousands of commercial truck drivers are illicit drug users” and that they have the drug testing data to back up their claims.
Based on the results of their findings, the Trucking Alliance recommended that more than 300,000 truck drivers be purged from the industry: “This survey can project as many as 301,000 commercial drivers would fail or refuse a hair test. These illicit drug users must be identified and taken out of commercial trucks and off the nation’s highways. The trucking industry has no greater safety issue, than to aggressively address illegal drug use among commercial truck drivers.”