CDL Endorsements Explained: H, N, P, S, T and X

What an endorsement is

49 CFR 383.93(a) says that on top of the regular knowledge and skills tests, anyone who drives or expects to drive certain vehicles must pass specialized tests to earn each endorsement, and that a state may issue the endorsement only to drivers who pass. 383.93(b) names the five vehicle types that need one: double/triple trailers, passenger vehicles, tank vehicles, vehicles carrying hazardous materials, and school buses. The codes printed on the license come from 49 CFR 383.153(a)(9).

• T: double/triple trailers
• P: passenger
• N: tank vehicle
• H: hazardous materials
• X: tank vehicle and hazardous materials combined
• S: school bus

Which tests each one needs

49 CFR 383.93(c) lays out the testing. Three endorsements are knowledge test only, and two also need a skills test.

• Double/triple trailers (T): knowledge test.
• Tank vehicle (N): knowledge test.
• Hazardous materials (H): knowledge test, plus the TSA check covered below.
• Passenger (P): knowledge test and a skills test.
• School bus (S): knowledge test and a skills test.
• X: the code for holding both tank vehicle and hazardous materials endorsements (383.153(a)(9)(v)), so you are cleared for both.

What each test covers

The topics are written into the regulation, which is why the practice questions look the way they do. Tank (383.119): cargo surge and how it affects handling, braking when the tank is empty, full or partly full, baffled versus unbaffled tanks, and the effect of grades and curves with different fill levels. Hazmat (383.121): the hazardous materials table, shipping papers, marking, labeling, placarding, loading and unloading, cargo segregation, parking and routes, and emergency response. Passenger (383.117): loading and unloading passengers, emergency exits, handling fires and unruly passengers, railroad crossings and drawbridges. The skills test has to be taken in a passenger vehicle of the group you want the endorsement for. School bus (383.123): you must first qualify for the passenger endorsement, then pass the school bus knowledge test and take a driving skills test in a school bus of the same vehicle group you will drive. Doubles and triples (383.115): hooking up the units, where the heaviest trailer goes, off-tracking, sway and rollover, and the problems a long rig creates for other traffic.

Hazmat is the one with a background check

Getting the H endorsement takes more than a test. 49 CFR 383.71(b)(8) requires hazmat applicants to comply with Transportation Security Administration requirements in 49 CFR part 1572, and a lawful permanent resident must also provide their USCIS Alien registration number. Part 1572 sets up a security threat assessment. Under 49 CFR 1572.15, it includes a fingerprint-based criminal history check and an intelligence-related background check. The applicant also pays a fee to TSA (1572.11(c)(2)). Under 1572.5, TSA can deny the endorsement for a disqualifying criminal offense listed in 49 CFR 1572.103, for not meeting the immigration status requirements, or for other security-threat findings. How you book fingerprinting, what the state adds on top, and how long it takes all depend on the state, so check with your licensing agency before you plan around a start date.

Permit limits and required training

Only three endorsements are allowed on a CLP: passenger (P), school bus (S) and tank vehicle (N). 49 CFR 383.93(a)(2) and 383.25(a)(5) say all other federal endorsements are prohibited on a permit. That means no H, T or X until you hold the CDL. An N on a permit lets you drive a tank vehicle only when it is empty, and not one that previously held hazardous materials and has not been purged of residue. A CLP holder also may not drive a CMV that is transporting hazardous materials (383.25(a)(6)). Training: since February 7, 2022, 49 CFR 383.71(a)(10) and (b)(11) require entry-level driver training from a provider on the FMCSA Training Provider Registry before you take the hazmat knowledge test for the first time, or the passenger or school bus skills test for the first time. States set their own test fees, scheduling and extra endorsement rules, so confirm the details with your state licensing agency.