CDL endorsements and restrictions explained
Every endorsement letter, the test and checks behind it, and every restriction code that can appear on a CDL, in plain words.
A CDL has two kinds of letters. Endorsements add something: the right to haul a tanker, carry passengers, pull doubles. Restrictions take something away: no air brakes, no manual gearbox, no driving out of state. Both appear on the licence card and both are checked at roadside inspections.
The six endorsements
| Code | Endorsement | Knowledge test | Other requirements |
|---|---|---|---|
| H | Hazardous materials | 30 questions, Section 9 of the manual | TSA security threat assessment with fingerprints, 21 for interstate, ELDT theory course, renewed every 5 years |
| N | Tank vehicles | 20 questions, Section 8 | None beyond the test |
| P | Passenger | 20 questions, Section 4 | Skills test in a passenger vehicle, ELDT |
| S | School bus | 20 questions, Section 10 | P endorsement first, skills test in a school bus, state background check, ELDT |
| T | Doubles and triples | 20 questions, Section 7 | Class A licence |
| X | Hazmat and tank combined | Both the H and N tests | Everything H requires |
H: hazardous materials
Needed to haul anything in quantities that require placards on the vehicle: fuel, chemicals, explosives, some gases. The test is the longest endorsement test and covers placarding, loading rules, the shipping papers and emergency response. The TSA check takes weeks, so start it before the test. The hazmat guide walks through it.
N: tank vehicles
Needed for any vehicle carrying liquid or gaseous cargo in a tank of 1,000 gallons or more, or in permanently or temporarily attached tanks over 119 gallons each adding up to 1,000 gallons. The test is about surge, baffles, outage and the way a half-full tank moves the vehicle. Tanker practice test.
P: passenger
Needed for any vehicle designed for 16 or more people including the driver: transit buses, coaches, shuttles. Covers loading, railroad crossings, braking and emergency exits. The skills test must be taken in a passenger vehicle. Passenger practice test.
S: school bus
On top of P. Covers loading and unloading children, the danger zones around the bus, the stop arm and emergency evacuation. States run their own background checks for school bus drivers. School bus practice test.
T: doubles and triples
Needed to pull more than one trailer. The test covers coupling converter dollies, the "crack the whip" effect and why the last trailer rolls over first. Triples are legal only in some western states. Doubles and triples practice test.
X: hazmat plus tank
One letter instead of two for drivers hauling hazardous liquids, such as fuel tanker drivers. You still sit both knowledge tests.
The restriction codes
| Code | Meaning | How it gets there |
|---|---|---|
| L | No full air brakes | Skipped the air brakes knowledge test, or tested in a vehicle without air brakes |
| Z | No full air brakes | Tested in a vehicle with air-over-hydraulic brakes |
| E | No manual transmission | Tested in an automatic |
| O | No tractor-trailer | Took the Class A test in a combination joined by a pintle hook, not a fifth wheel |
| M | Class A holder limited to Class B or C passenger vehicles | Took the passenger skills test in a smaller bus |
| N | Class B holder limited to Class C passenger vehicles | Took the passenger skills test in a Class C vehicle |
| K | Intrastate only | Under 21, or self-certified for in-state driving only |
| V | Medical variance on record | FMCSA has granted an exemption, for vision, hearing, diabetes or a limb |
Restrictions that come from the vehicle you tested in (L, Z, E, O, M, N) can be removed by retaking the skills test in a vehicle without that limitation. L can also be removed by passing the air brakes knowledge test, in states that allow it, when the restriction came from skipping the test alone. K lifts at 21 or when you change your self-certification and meet the medical requirement.