Which CDL Endorsements Do I Need? Air Brakes, Tanker, Hazmat, and More

Northlight Publishing · Updated September 2026

A Class A or B CDL gets you in the door. Endorsements decide which loads you can actually haul, and they have a direct effect on pay and job options. Here is what each one does.

Air brakes

Technically this is a restriction removal rather than an endorsement: without passing the air brakes test, you are restricted from driving vehicles with air brakes, which rules out most heavy trucks. Almost every driver should take it. The test is usually 25 questions.

Combination vehicles

Required for a Class A license, which covers tractor-trailers. Usually 20 questions.

Doubles and triples (T)

Lets you pull double or triple trailers, common in LTL freight. Usually 20 questions.

Tank vehicles (N)

Required to haul liquids or gases in tanks above certain capacities. Tanker work often pays more, and the test covers surge, baffles, and outage. Usually 20 questions.

Hazardous materials (H) and X

Hazmat requires a knowledge test, usually 30 questions, plus a TSA security threat assessment with fingerprints, so start the background check early. Hazmat plus tanker together form the X endorsement, which fuel haulers need.

Passenger (P) and school bus (S)

These are for bus drivers and require skills tests in addition to knowledge tests.

Which ones should you get?

For most new Class A drivers: air brakes and combination are mandatory in practice, and doubles/triples plus tanker are cheap to add while you are already studying. Hazmat is worth it if you are targeting fuel, chemical, or higher-paying freight, but plan for the TSA timeline.

The CDL Endorsements Study Pack covers all five knowledge tests in one printable pack, with practice sets matched to real test lengths and a numbers section with every psi, foot, and pound. If you have not yet passed the general knowledge test, start with the CDL General Knowledge Test Prep.