Endorsements
What endorsements add
Endorsements are add-on authorizations; they do not change your CDL class. Idaho general knowledge exams include endorsement-specific questions. P is required to drive a CMV designed to carry 16 or more passengers, including the driver; it also requires a skills test in a passenger vehicle. S is the school-bus endorsement, which builds on P and adds school-bus knowledge and skills. N is required for tank vehicles: a CMV that carries liquid or gaseous material in a tank with individual capacity over 119 gallons and aggregate capacity of 1,000 gallons or more. H is required for hazardous materials that require placards; it requires a TSA security threat assessment before issuance. X combines H and N.
Tests and limits
T is the double/triple trailer endorsement; it requires the knowledge test and authorizes towing doubles or triples, not a single trailer. H requires the hazardous-materials knowledge test and TSA clearance; a candidate cannot simply add H by paying a fee. P and S require knowledge and skills. The tank endorsement is not a generic “I hauled a tank” permission-capacity and design matter.
Worked example
A Class A driver wants to pull a 3,500-gallon cargo tank carrying placarded gasoline. The vehicle needs N because it is a tank vehicle over the capacity thresholds, and H because the gasoline is placarded. The combination is shown as X (H+N). The driver must pass the tank and hazmat knowledge tests and obtain TSA clearance; the Class A license alone is not enough.
Traps
Do not assume H covers tank vehicles or that N covers placarded cargo. Do not count a portable tank's contents by weight; the rule uses tank capacity. P is not required for a 15-passenger van (15 including driver) unless another rule applies. T does not authorize triples in every State or on every route; route/vehicle limits still apply.