CDL Endorsements Explained
Your CDL by itself only allows you to drive a basic commercial vehicle. To haul HAZMAT, drive a tanker, pull doubles, transport passengers, or operate a school bus, you need additional endorsements. Each endorsement is a separate test (and in some cases a separate background check) that gets stamped onto your license.
Endorsements directly affect your earning potential. A driver with HAZMAT and Tanker (the X endorsement) can haul fuel — one of the highest-paying local CDL jobs. A driver with Passenger and School Bus has access to school district jobs with benefits and predictable hours. Picking the right endorsements for your career is one of the most important decisions you'll make as a new driver.
The full list
- H — HAZMAT. Required to haul hazardous materials. Includes a TSA background check.
- N — Tanker. Required for liquid or gas tank vehicles over 1,000 gallons.
- T — Doubles / Triples. Required to pull two or three trailers.
- P — Passenger. Required for vehicles carrying 16+ passengers including the driver.
- S — School Bus. Required to drive a school bus. Requires P first, plus state background checks.
- X — HAZMAT and Tanker combined. Take both H and N tests; appears on your license as X.
HAZMAT (H)
The HAZMAT endorsement is the most lucrative single endorsement, and the most paperwork-heavy. Beyond the written test, you must complete a TSA background check that takes 30 to 60 days to clear. Disqualifying convictions include felonies involving explosives, terrorism, treason, or transportation security incidents.
Test content covers the nine DOT hazard classes, placarding, shipping papers, segregation rules, loading and unloading, parking restrictions, and emergency response. The HAZMAT test is about 30 questions — longer than most endorsement tests — at 80% to pass.
Best for: drivers who want higher pay and don't have disqualifying convictions, who can wait through the TSA process, and who don't mind the additional regulatory scrutiny.
Take the HAZMAT practice test →
Tanker (N)
The Tanker endorsement is required for any commercial vehicle transporting bulk liquids or gases in a tank with capacity over 1,000 gallons. The test focuses on the unique handling characteristics of tank vehicles — liquid surge, high center of gravity, baffled vs. smooth bore tanks, and inspection requirements.
Tanker work spans many products: fuel, milk, water, chemicals, food-grade liquids. Some products require additional certifications beyond the CDL Tanker endorsement (food-grade transport, for example, requires sanitation training). Pay is generally higher than dry van or flatbed work.
Best for: drivers who want a focused niche, who can drive smoothly (tanker drivers must brake gently and corner slowly), and who don't mind the added inspection time.
Take the Tanker practice test →
Doubles / Triples (T)
The T endorsement allows you to pull two or three trailers in combination. Doubles are common across the western and central United States, especially for less-than-truckload (LTL) freight where multiple short trailers can be efficiently swapped at terminals. Triples are legal in fewer states and on fewer routes.
Test content covers coupling and uncoupling sequences (which differ from a standard tractor-trailer), converter dolly inspection, weight order rules (heaviest trailer goes first), and the unique handling characteristics of multi-trailer combinations — especially "crack-the-whip" trailer swing.
Best for: drivers working LTL freight networks (think YRC, Old Dominion, Estes, FedEx Freight) and drivers in western states where doubles are common.
Take the Doubles/Triples practice test →
Passenger (P)
The P endorsement is required for any commercial vehicle designed to carry 16 or more passengers including the driver. That covers transit buses, charter buses, intercity coaches, airport shuttles, and tour buses. The endorsement does not in itself qualify you to drive a school bus — that's a separate S endorsement.
Test content focuses on loading and unloading procedures, emergency exits and evacuation, prohibited cargo, special handling for disorderly passengers, and the railroad-crossing rules that apply to all buses.
Best for: drivers who prefer dealing with people over freight, who can drive smoothly enough to keep standing passengers comfortable, and who want the flexibility of charter, tour, or transit work.
Take the Passenger practice test →
School Bus (S)
The S endorsement allows you to drive a school bus. It's the most regulated CDL endorsement in the United States. To get it, you must already hold (or simultaneously obtain) the P endorsement, pass the school bus written test, pass a school bus skills test in an actual school bus, and pass state-specific background checks.
Test content focuses on the danger zone (10 feet around the bus), loading/unloading procedures with red lights and stop arms, mandatory railroad crossing stops, emergency evacuation decision-making, and post-route inspection (walking the bus to ensure no children are left behind).
Best for: drivers who want predictable hours and benefits (most school bus driver jobs are with school districts and include healthcare and retirement), who have a clean driving record, and who pass the additional state-level scrutiny.
Take the School Bus practice test →
X — HAZMAT plus Tanker
X isn't a separate test. If you pass both the HAZMAT and Tanker tests, your CDL displays X instead of H and N separately. The X endorsement signals you can haul hazardous liquids in tanks — fuel, primarily — which is one of the highest-paying local CDL jobs. Fuel haulers, propane delivery drivers, and chemical tanker operators all need X.
Best for: drivers who want the highest local-driving pay tier, who can pass the TSA background check, and who can manage the dual safety responsibility of HAZMAT plus tanker.
Restrictions vs. endorsements
Endorsements add capabilities to your CDL. Restrictions remove them. The most common restrictions:
- L — No air brakes. If you didn't take or pass the air brake test, you can't drive a vehicle with air brakes. This is a major career limit.
- Z — No full air brake systems. If you took your skills test in a vehicle with air-over-hydraulic brakes instead of full air brakes.
- E — No manual transmission. If you took your skills test in an automatic, you can't drive a manual.
- O — No tractor-trailer. If you took your Class A skills test in a non-fifth-wheel combination.
- M — No Class A passenger vehicle. Specific to certain bus configurations.
- N — No Class A or B passenger vehicle. Same.
Many drivers learn this the hard way: they take the easy path on their skills test (automatic transmission, no air brakes), then find out their license has a restriction that prevents them from getting hired for many jobs. Test in the vehicle that matches what you'll actually drive.
Endorsement combinations and pay
Your earning potential as a CDL driver scales with the endorsements you hold and the kind of work you take. Some general patterns:
- Class A only: Entry-level dry van and flatbed. Lowest pay tier.
- Class A + HAZMAT: Some chemical and industrial freight. Modest pay bump.
- Class A + Tanker + HAZMAT (X): Fuel hauling, chemical tanker. Major pay tier above general freight.
- Class A + Doubles/Triples: LTL freight networks. Stable, often union, mid-tier pay.
- Class B + Passenger + School Bus: School district work. Lower per-mile pay but predictable hours and benefits.
- Class B + Passenger: Charter, tour, transit. Variable pay depending on operator.
Take the practice tests
Every endorsement on this page has a free practice test on MyCDLPractice. Pick the ones that match your career path and start practicing.