Every driver who maintains a commercial driver's license or who operates a commercial vehicle for interstate commerce that meets certain restrictions must have a DOT medical card to legally drive. Drivers of vehicles that are above a certain weight, carry a certain number of people or are used for hazardous materials all qualify.
There are five instances in which drivers operating commercial vehicles for interstate commerce must have a current DOT medical card to legally drive. The first is when the vehicle has a combined gross vehicle weight or a weight rating of at least 10,001 pounds. The second and third pertain to drivers operating vehicles designed or used to transport large numbers of people. The driver must have a DOT medical card if the vehicle is meant to transport nine to 15 people, including the driver, for compensation. A driver must also have a DOT medical card if the vehicle is meant to transport 16 or more passengers including himself, regardless of compensation.
Vehicles that transport hazardous materials in quantities that require placarding under hazardous materials regulations are the fourth reason for a driver to have a DOT medical card to legally drive. The fifth instance is when a driver is returning from an illness or injury that has previously prevented him from working.
A DOT medical card is given after a driver has passed a DOT medical examination. The driver must retake the exam even if the current DOT card would otherwise still be valid if he is returning from illness or injury.