There are three million commercial truck drivers in the United States. Once the hazardous material program was instituted by TSA, many of them decided not to go through the process to haul hazardous materials. About 30% of all commercial drivers have applied for the HAZMAT endorsement. Those who did not can only carry regular goods, non-hazardous goods. They have to conduct the security threat assessment and apply for this program to haul hazardous materials. So most of the nation's truck drivers, commercial drivers, are not hazardous material qualified.
On March 5th, 2009. See this statement in context.