- NH-CDL Exam Overview: How the Knowledge Test Works
- Domain 1: General Knowledge
- Domain 2: Air Brakes
- Domain 3: Combination Vehicles
- Domain 4: Tank Vehicles
- Domain 5: Passenger Transport
- Domain 6: Doubles and Triples
- Domain 7: Hazardous Materials
- Domain 8: School Bus
- Which Domains Do You Actually Need?
- Scheduling the Eight Domains Into a Study Plan
- Fees and Timing Tied to Each Domain
- FAQ
- The NH-CDL knowledge exam has up to 50 multiple-choice questions with a 60-minute limit.
- You need 80% correct to pass, and a passing result stays valid for one year.
- Only Domain 1 (General Knowledge) and Domain 2 (Air Brakes) are required for every applicant; the other six depend on your vehicle and cargo plans.
- Your Commercial Learner Permit must be held at least 14 days before any skills test, regardless of which domains you completed.
NH-CDL Exam Overview: How the Knowledge Test Works
Before diving into the eight content areas, it helps to understand the mechanics of the New Hampshire CDL Permit Test itself. This isn't a private certification exam administered by an outside testing company - it's run directly by the New Hampshire Division of Motor Vehicles, Department of Safety. That matters because your domain selection, fees, and scheduling all flow through the same state agency, with no separate vendor accounts or third-party proctoring platforms to juggle.
The knowledge test itself contains up to 50 multiple-choice questions, and you're given up to 60 minutes to complete it. You need to score 80% or better to pass, and once you pass, that result is valid for one year - plenty of time to schedule and complete your skills test, provided you've also held your Commercial Learner Permit for at least 14 days. For a full breakdown of exactly how the passing threshold is calculated, see our NH-CDL Passing Score 2026 guide.
Each of the eight domains below corresponds to a distinct knowledge test you may need to take, depending on the class of CDL and endorsements you're pursuing. If you haven't yet mapped out which combination applies to you, our NH-CDL Requirements guide is a good starting point before you commit study time to any single domain.
Domain 1: General Knowledge
General Knowledge
This is the foundation domain every CDL applicant must pass, regardless of vehicle class or endorsement goals. It covers the baseline rules of operating a commercial motor vehicle safely on New Hampshire roads.
- Vehicle inspection procedures and identifying safety defects before driving
- Basic control system operation: shifting, backing, and turning a commercial vehicle
- Safe driving practices, including speed management, space management, and night driving
- Recognizing and responding to hazardous driving conditions
- Basic emergency maneuvers and accident procedures
Because General Knowledge underlies everything else, it's the natural first stop in any study plan. Our NH-CDL Study Guide 2026 walks through how to structure your review of this domain before moving to more specialized content.
Domain 2: Air Brakes
Air Brakes
Required if you plan to drive a vehicle equipped with air brakes - which describes the majority of commercial trucks and buses. Skipping this domain restricts your CDL to vehicles without air brake systems.
- Air brake system components: compressor, reservoirs, and brake chambers
- Dual air brake systems and how they differ from single systems
- Proper inspection sequence for checking air pressure buildup and warning devices
- Low air pressure warnings and what triggers the spring brakes
- Stopping distances and how air brake lag affects them
Candidates often underestimate how technical this domain feels compared to General Knowledge. If you're trying to gauge overall difficulty across the full test, our How Hard Is the NH-CDL Exam? guide breaks down where most applicants lose points.
Domain 3: Combination Vehicles
Combination Vehicles
This domain applies to anyone pursuing a Class A CDL - tractor-trailers and other combination rigs. It builds directly on General Knowledge but focuses on the added complexity of towing.
- Coupling and uncoupling procedures for tractor-trailer combinations
- Combination vehicle inspection points unique to trailers and connections
- Handling characteristics: off-tracking, rearward amplification, and splash/spray
- Antilock brake systems on combination vehicles
Domain 4: Tank Vehicles
Tank Vehicles
Needed for the tank vehicle endorsement, this domain addresses the unique physics and safety concerns of hauling liquids or gases in bulk.
- Effects of liquid surge on handling and braking
- Baffled versus unbaffled tanks and how that affects vehicle stability
- Weight distribution and rollover risk specific to partially filled tanks
- Inspection requirements specific to tank vehicles
Domain 5: Passenger Transport
Passenger Transport
Required for the passenger endorsement, this domain shifts focus from cargo to people - loading, securing, and responding to emergencies with riders on board.
- Safe loading and unloading procedures at stops
- Emergency exit and evacuation procedures
- Passenger management, including standees and prohibited items
- Use of mirrors and communication with passengers while driving
Domain 6: Doubles and Triples
Doubles and Triples
This domain is required for the doubles/triples endorsement and covers the added handling risks of pulling more than one trailer.
- Coupling and uncoupling sequences for multiple trailers
- Inspecting converter dollies and additional connection points
- Handling differences: increased rearward amplification and crack-the-whip effect
- Proper use of trailer hand valves and emergency procedures
Domain 7: Hazardous Materials
Hazardous Materials
Required for the HazMat endorsement, this is widely regarded as one of the more detail-heavy domains because it draws on federal shipping and placarding rules.
- Shipping paper requirements and hazard class identification
- Placarding rules and table-based placarding requirements
- Loading, unloading, and segregation rules for incompatible materials
- Emergency response basics and driver responsibilities in an incident
Domain 8: School Bus
School Bus
Required for the school bus endorsement, layered on top of the passenger transport knowledge above, with rules specific to transporting students.
- Student loading and unloading procedures, including the use of the stop signal arm
- Railroad-highway grade crossing procedures for school buses
- Emergency evacuation drills specific to student passengers
- Danger zones and mirror use around the bus
Which Domains Do You Actually Need?
Not every applicant tests on all eight domains. The two constants are General Knowledge and, for most vehicles, Air Brakes. Everything else depends on the class of license and endorsements you're pursuing. A driver aiming for a straight Class B box truck job may only need Domains 1 and 2, while someone targeting tanker or HazMat freight will stack multiple domains onto the same permit process.
| Domain | Who Needs It | Typical Trigger |
|---|---|---|
| General Knowledge | All applicants | Any CDL class |
| Air Brakes | Most applicants | Vehicle equipped with air brakes |
| Combination Vehicles | Class A applicants | Tractor-trailer operation |
| Tank Vehicles | Tank endorsement seekers | Hauling bulk liquids/gases |
| Passenger Transport | Passenger endorsement seekers | Buses, shuttles, transit |
| Doubles and Triples | Multi-trailer operators | Pulling more than one trailer |
| Hazardous Materials | HazMat endorsement seekers | Transporting regulated materials |
| School Bus | School bus endorsement seekers | Transporting students |
Understanding this mapping early saves wasted study hours. If you're weighing whether stacking multiple endorsements is worth the added prep time relative to job opportunities, our Is the NH-CDL Certification Worth It? analysis and NH-CDL Jobs overview both address that from a career-planning angle.
Scheduling the Eight Domains Into a Study Plan
Because each domain is a separate knowledge test with its own question bank, treating them as isolated study blocks - rather than one big undifferentiated review - tends to produce better results. A simple approach is to sequence domains by dependency and difficulty: start with the domain everyone needs, then layer in vehicle-specific and cargo-specific domains in the order you'll actually test on them.
General Knowledge
- Work through inspection procedures and basic control systems
- Take practice questions daily to build familiarity with the multiple-choice format
Air Brakes
- Focus on dual air systems and warning device thresholds
- Review this domain even if uncertain about final vehicle assignment - most fleets run air brakes
Endorsement-Specific Domains
- Add Combination Vehicles, Tank Vehicles, Passenger Transport, Doubles/Triples, HazMat, or School Bus based on your target job
- Study only the domains relevant to your license class to avoid wasted effort
Full Review and Scheduling
- Take timed practice runs matching the 60-minute, 50-question format
- Confirm your CLP timing so it's held 14 days before any skills test
For a condensed version of this plan you can review the night before test day, bookmark the NH-CDL Cheat Sheet 2026. And if you want to see how your prep timeline should interact with actual DMV scheduling windows, check NH-CDL Exam Dates 2026.
Key Takeaway
Study General Knowledge and Air Brakes first since nearly every applicant needs them, then add only the specialized domains tied to your intended endorsements - don't waste hours on domains you won't test on.
Fees and Timing Tied to Each Domain
Domain selection has direct cost implications. The Commercial Learner Permit itself costs $20, and an original or renewed CDL - including the examination - costs $60. If you're adding endorsements or removing a restriction later, each one runs $10. Testing on more domains up front, when you're already paying the CDL and examination fee, is generally more efficient than returning later to add endorsements individually.
Keep in mind that your CDL doesn't require re-testing on these domains indefinitely - it remains valid until it expires on your birthday in the fifth year after issuance, provided your medical certification stays current. But if your knowledge test passing result lapses before you complete skills testing, since it's only valid for one year, you may need to retest on the relevant domains. For the full fee schedule broken out line by line, see our NH-CDL Certification Cost 2026 breakdown.
If any of the terminology in this guide - CLP, endorsement, restriction - still feels unfamiliar, our foundational explainers cover the basics: What Is NH-CDL?, NH-CDL Meaning, and What Does NH-CDL Stand For? all address common points of confusion for first-time applicants. For a more complete look at how this credential fits into a driving career, NH-CDL Training and NH-CDL Salary Guide 2026 are worth reading alongside this domain breakdown, and you can start practicing questions across all eight domains right on the main practice test site.
Frequently Asked Questions
No. General Knowledge is required for every applicant, and Air Brakes applies to nearly all vehicles. The remaining six domains - Combination Vehicles, Tank Vehicles, Passenger Transport, Doubles and Triples, Hazardous Materials, and School Bus - are only required if you're pursuing the matching license class or endorsement.
The knowledge examination format allows up to 50 multiple-choice questions with up to 60 minutes to complete it, and you need 80% correct to pass. This format applies to the knowledge tests administered by the New Hampshire DMV.
A passing result remains valid for one year. You'll also need to hold your Commercial Learner Permit for at least 14 days before taking any related skills test, so plan your domain testing with that window in mind.
Yes. Each additional endorsement or restriction removal costs $10, which typically means retesting on the relevant knowledge domain before the endorsement is added to your license.
Start with General Knowledge since it's required for everyone and underpins the other domains, then move to Air Brakes, followed by whichever specialized domains match your target vehicle class and endorsements.