CDL (Class A / B)

Exam blueprint

Sourced from FMCSA 49 CFR Part 383 + AAMVA Model CDL Manual + Each State's CDL Manual (varies)

• General knowledge — laws, rules, vehicle classification20%
• Air brake systems — operation, inspection, leak limits20%
• Pre-trip inspection — engine, in-cab, trailer, brake check20%
• Basic vehicle control — backing, alley dock, parallel park10%
• On-road driving — speed, space management, hazards10%
• Class A combination vehicles — coupling, uncoupling10%
• Endorsements — T, N, H, P/S basics10%

1. 01General knowledge — what every CDL driver must know

   ~90min

   The general-knowledge written test is required for all CDL classes. Covers vehicle classification, BAC limits, medical certification, and the federal disqualifications that strip a CDL.

   • Class A / B / C — the GVWR/GCWR rules

     GVWR (Gross Vehicle Weight Rating) is the manufacturer's rated max weight of the vehicle alone. GCWR (Gross Combination Weight Rating) is the rated max weight of the vehicle PLUS the trailer/towed unit. CLASS A: GCWR ≥ 26,001 lb AND towed unit GVWR > 10,000 lb. CLASS B: single-vehicle GVWR ≥ 26,001 lb (with or without a towed unit ≤ 10,000 lb). CLASS C: anything <26,001 lb that carries 16+ passengers or placardable hazmat. Construction examples: a tri-axle dump truck pulling a pup trailer (>10,000 lb) is Class A. A standalone tri-axle dump (no trailer) is Class B. A 1-ton service truck pulling a 14-ft trailer (typically <10,000 lb) requires no CDL at all if the combination is <26,001 lb GCWR.

     Reference: 49 CFR 383.91 (Commercial Motor Vehicle Groups)

   • BAC limits + DOT medical card

     CDL drivers operate under STRICTER alcohol rules than other drivers: 0.04% BAC is the legal limit while operating a CMV (vs 0.08% non-CDL). Refusing a chemical test = automatic disqualification for 1 year (3 years if hazmat). Drivers must hold a current DOT MEDICAL CARD (Medical Examiner's Certificate, MCSA-5876) issued by a National Registry-certified examiner. Standard certification is 2 years; certain conditions (insulin-controlled diabetes, sleep apnea on CPAP, certain cardiac conditions) reduce that to 1 year or less and may require a federal exemption. Self-certification of driver type (interstate non-excepted, etc.) is filed with the state CDL section.

     Reference: 49 CFR 383.51 + 391.41 (Medical)

   • Major + serious traffic offenses

     Major offenses (1-year disqualification, 3-year if hazmat, lifetime for two): DUI, refusing alcohol/drug test, leaving the scene of an accident, using a CMV to commit a felony, driving with a revoked/suspended/cancelled CDL. Serious traffic offenses (60-day disqualification on second within 3 years, 120-day on third): excessive speeding (>15 mph over), reckless driving, improper lane changes, following too closely, texting while driving in a CMV (CDL-only offense), no CDL in possession. These rules apply ON OR OFF DUTY, ON OR OFF the CMV — a DUI in your personal car kills your CDL. Most CDL holders never read this section until it is too late.

     Reference: 49 CFR 383.51 (Disqualifications)

   Practice questions (2)

   1. 1. A construction company operates a tri-axle dump truck (GVWR 54,000 lb) pulling a pup trailer with GVWR 12,000 lb. Which CDL class is required?

      • A.Class C
      • B.Class B
      • C.Class A✓ correct
      • D.No CDL — under 26,001 lb GCWR

      Combined GCWR is 66,000 lb (well over 26,001) AND the towed unit GVWR is 12,000 lb (over 10,000). Both Class A criteria met. Class B applies to a single vehicle ≥26,001 lb (no trailer, or trailer ≤10,000 lb). Class C is for small CMVs with passenger or hazmat triggers. The "no CDL" option is implausible — the truck alone is over 26,001 lb.

   2. 2. A CDL driver is involved in an off-duty single-car DUI in their personal vehicle (BAC 0.10%). Effect on CDL?

      • A.No effect — it was off-duty in a personal vehicle
      • B.1-year CDL disqualification (3 years if hazmat) — major offense rule applies on or off duty✓ correct
      • C.60-day disqualification only
      • D.Penalty only if BAC was over 0.04%

      49 CFR 383.51 disqualifications apply ON OR OFF DUTY, in CMV or personal vehicle. A DUI conviction is a "major offense" → 1-year CDL disqualification (3 years if the driver had a hazmat endorsement). The 0.04% threshold applies WHILE OPERATING A CMV, but a personal-vehicle DUI uses the state's civilian limit (0.08% in most states) — once convicted, the federal CDL disqualification is automatic.

2. 02Air brakes — operation, inspection, leak limits

   ~90min

   Almost every construction CDL truck has air brakes. Pass the air-brake knowledge test PLUS demonstrate air-brake checks during the pre-trip and skills test, or you get an "air brake restriction" stamp that limits you to non-air-brake CMVs (rare in construction, so never accept the stamp).

   • How the air system works

     COMPRESSOR pumps air from atmosphere; GOVERNOR cycles the compressor on and off (cuts in around 100 psi, cuts out around 125 psi typical). Air dries in an AIR DRYER and is stored in PRIMARY + SECONDARY (and supply) RESERVOIRS. From there, air goes to the SERVICE BRAKES via the foot valve and to the SPRING BRAKES (parking/emergency) via a separate circuit. The GLAD HANDS connect tractor to trailer with two lines: SERVICE (control) and EMERGENCY (supply). Loss of pressure in the supply line automatically applies the trailer's spring brakes — that is the FAIL-SAFE. Drivers must understand this because every air-brake test question is rooted in the system layout.

   • Allowable leak rates and warning levels

     STATIC LEAK TEST (engine off, brakes released): single-vehicle leak ≤ 2 psi per minute; combination ≤ 3 psi per minute. APPLIED LEAK TEST (engine off, fully apply foot valve, hold): single ≤ 3 psi/min; combination ≤ 4 psi/min. LOW-AIR WARNING: must trigger at or before 60 psi (light + buzzer). EMERGENCY (SPRING) BRAKE APPLICATION: must apply at no less than 20-45 psi range — typically around 20-40 psi as the system bleeds down. Memorize: 2 / 3 / 3 / 4 / 60 / 20-40. The exam will hand you a leak number and ask "is this within the allowable rate?" — math is simple if the limits are memorized.

     Reference: 49 CFR 393.50 + state CDL Manual air-brake section

   • Stab braking, controlled braking, and brake fade

     CONTROLLED BRAKING: hold the brake pedal at constant pressure with the wheels JUST short of locking. Used for normal panic stops on a vehicle without ABS. STAB BRAKING: fully apply, fully release, fully apply — used when wheels start to lock without ABS, or when the vehicle starts a jackknife slide. ABS-equipped trucks: just press hard and hold; the ABS modulates for you. BRAKE FADE on long downgrades occurs when brakes overheat and lose effectiveness. Prevent it by pre-selecting a low gear DESCEND, using the engine brake/jake brake, and using SNUB braking (apply firmly to slow ~5 mph, then release for cooling) rather than continuous light pressure.

   Practice questions (2)

   1. 1. During a static air leak test on a tractor-trailer combination, the gauge drops from 100 psi to 96 psi over 60 seconds. Acceptable?

      • A.Yes — under the 5 psi/min single-vehicle limit
      • B.No — combination static-leak limit is 3 psi/min; 4 psi/min fails✓ correct
      • C.Yes — combination limit is 4 psi/min
      • D.No — any leak is a failure

      For a combination vehicle, the STATIC (engine-off, brakes released) leak limit is 3 psi per minute. A 4 psi drop in 60 seconds is over that limit and fails. The 4 psi/min figure is the APPLIED leak limit (foot brake fully applied), not static. Some leakage is allowed — small leaks are normal — but the rate must stay below the limits.

   2. 2. On a CDL skills test, the examiner asks at what pressure the low-air warning should activate. Correct answer?

      • A.Anytime below 100 psi
      • B.At or before 60 psi✓ correct
      • C.At 20-40 psi
      • D.Only when the spring brakes apply

      FMCSA standards require the low-air warning (light + buzzer) to activate AT OR BEFORE 60 psi. The 20-40 psi range is when the spring brakes (parking/emergency) automatically apply due to insufficient air pressure to keep them released — that comes AFTER the warning. 100 psi is roughly the cut-in pressure, not a warning trigger.

3. 03Pre-trip inspection — the memorization marathon

   ~180min

   The pre-trip is the most-failed component of the CDL skills test. ~120 items to inspect on a Class A combination, in a memorized order, calling them out aloud while pointing. Memorize the SEQUENCE first, then the WHAT and the WHY for each item.

   • Engine compartment — top to bottom, left to right

     Standard sequence: oil dipstick (level + condition), coolant reservoir (level), windshield washer, power steering reservoir, alternator (mounted secure, belt 1/2 to 3/4 in deflection, no cracks/frays), water pump (mounted secure, no leaks), air compressor (mounted secure, gear-driven OR belt-driven — note which), engine mounts, leaks (fuel, oil, coolant, hydraulic), steering box / sector shaft (mounted secure, no leaks), steering linkage, drag link / pitman arm. Each item: state the part, state what you check (mounted secure / no cracks / no leaks / proper level), point as you call it. Examiner is not testing technical depth — they are testing thoroughness and order.

   • Front axle, brakes, and steering

     Front axle: tires (matched size, dual matched if duals; tread depth ≥4/32 on steer axles, ≥2/32 on others; no major cuts, sidewall damage, or exposed cord); rims (no bends, cracks, missing/loose lug nuts, rust trails indicating loose lugs); hub oil seal (level + no leaks); brakes — DRUM brakes: drum (no cracks larger than half the width or extending into the open end), shoes/linings (≥1/4 in remaining, no contamination), brake chamber (mounted secure, no audible leaks), slack adjuster (≤1 in free travel when pulled by hand with brakes off); air lines (no leaks, properly secured, no abrasion). For DISC brakes: rotor + caliper inspection. Memorize the specific limit numbers — examiners ask them.

     Reference: 49 CFR 393.75 (Tires) + 393.47 (Brake System Components)

   • In-cab inspection + 7-step air brake check

     In-cab: emergency equipment (3 reflective triangles, fire extinguisher minimum 5 BC rated, spare electrical fuses unless circuit breakers), seat belt, mirrors, windshield (no cracks in driver line of sight), wipers, horn, parking brake (set), gauges (oil pressure 30-75 psi running, water temp 165-185, fuel, voltmeter 13-14V), heater/defroster, dome light. THEN the 7-STEP AIR BRAKE CHECK: (1) governor cut-out (build to 125 psi, check compressor cycles); (2) governor cut-in (pump down to ~100 psi, watch for re-engagement); (3) air pressure builds 85-100 psi in 45 seconds; (4) low-air warning at or before 60 psi; (5) spring brakes apply at 20-40 psi; (6) static leak test (≤2 single, ≤3 combination); (7) applied leak test (≤3 single, ≤4 combination). Memorize this sequence cold — examiners deduct points for skipping or scrambling order.

   • Coupling system + trailer — Class A only

     CLASS A only: fifth wheel (mounted secure, no cracks, properly greased), kingpin (locked into fifth wheel jaws, no daylight visible between trailer and fifth wheel), apron (no cracks), safety latch / locking jaw closed, glad hands (service + emergency, properly seated, no cracked seals), air lines + electrical lines (secure, no rubbing, no leaks), landing gear (fully retracted, no damage), trailer brakes + lights + tires + frame + load (load secure if applicable). Show the examiner you are physically touching/tugging the kingpin lock and confirming visually — this is one of the most-deducted items. The "tug test" is non-negotiable.

   Practice questions (2)

   1. 1. During pre-trip inspection of a steer-axle tire, the candidate finds the tread depth at 3/32 inch. Action?

      • A.Acceptable — over the 2/32 minimum
      • B.Reject the vehicle for service — steer-axle minimum tread depth is 4/32 inch✓ correct
      • C.Acceptable if the other tire has more tread
      • D.Acceptable for in-town driving only

      FMCSA 49 CFR 393.75 sets the minimum tread depth at 4/32 inch on STEER AXLES (front) and 2/32 inch on all others. 3/32 fails the steer-axle minimum and is an out-of-service condition — the vehicle cannot be driven. The other-tire-has-more-tread answer (option C) is wrong because each tire is judged individually. There is no in-town exemption.

   2. 2. After coupling a tractor to a trailer, what is the proper "tug test" sequence to confirm the kingpin is locked?

      • A.Visually inspect only — no tug test required
      • B.Set trailer brakes only, drive forward gently to confirm trailer pulls with tractor
      • C.With trailer brakes set, gently put tractor in low gear and apply slight forward pressure; trailer should not separate✓ correct
      • D.Disconnect glad hands and pull forward to verify

      The standard tug test: set the TRAILER brakes (red knob in / parking valve), put the tractor in low forward gear, gently apply throttle and let the clutch out enough to put load on the kingpin. If the kingpin is properly locked, the tractor will resist or stop — the rig is together. If improperly locked, the tractor will pull AWAY from the trailer. Visual inspection alone is insufficient. Disconnecting glad hands intentionally is dangerous and not part of the test.

4. 04On-road driving + basic control

   ~90min

   After pre-trip and air brakes, the skills test moves to backing maneuvers (alley dock, offset back, parallel park) and on-road driving. Examiners watch traffic checks, lane discipline, and brake/clutch coordination.

   • Backing — straight-line, alley dock, offset, parallel

     STRAIGHT-LINE BACK: pull forward in a straight line, then back straight without crossing boundary cones. Use both mirrors equally. Pull-ups are allowed but cost points — use as few as possible. ALLEY DOCK: parallel to a row of parked-truck cones, then back into a 90° dock. Setup is everything — a poor pull-forward setup makes the back-in nearly impossible. OFFSET BACK: pull forward, then back into a parallel space offset to your left or right by one lane width. PARALLEL PARK (driver-side or passenger-side, sometimes called "sight-side" or "blind-side"): back into a curb-side parking box. Blind-side is harder — pull forward 30° more than you think you need, then steer-and-correct. GET OUT AND LOOK (G.O.A.L.) is allowed and ENCOURAGED — examiners would rather see two GOALs than one curb hit.

   • Space management on the road

     FOLLOWING DISTANCE: 1 second per 10 ft of vehicle length at speeds ≤40 mph; add 1 second above 40 mph. A 60-ft Class A combination at 55 mph needs 7+ seconds. STOPPING DISTANCE: at 55 mph on dry pavement, total stopping distance for a fully loaded CMV is roughly 300 ft (~6 seconds reaction + braking) — much longer than a passenger car. SPACE TO THE SIDES: don't drive in another vehicle's blind spot ("No-Zones" around CMVs). SPACE OVERHEAD: know your loaded height; bridges as low as 11'-6" exist. SPACE BELOW (low railroad crossings, weight-restricted bridges): scan ahead. The exam will phrase questions as "what is the proper following distance for a 50-ft combination at 50 mph?" Calculate: 5 seconds (for 50 ft at ≤40 mph) + 1 (over 40) = 6 seconds.

   Practice questions (1)

   1. 1. A 65-foot tractor-trailer is traveling at 50 mph. Recommended minimum following distance per the AAMVA Model CDL Manual?

      • A.3 seconds
      • B.5 seconds
      • C.7 seconds
      • D.8 seconds✓ correct

      Rule: 1 second per 10 ft of vehicle length at ≤40 mph; ADD 1 second above 40 mph. For a 65-ft rig: 65/10 = 6.5, round up to 7 seconds at lower speed. At 50 mph (above 40), add 1 more second: 8 seconds total. The 5- and 7-second options miss the over-40 mph bump. 3 seconds is the rule for passenger cars.

5. 05Endorsements — T, N, H + others

   ~75min

   Construction-relevant endorsements. T (doubles/triples), N (tank), and H (hazmat) require additional written exams. H additionally requires a TSA background check under 49 CFR 1572 — fingerprints, biometric clearance, and renewal.

   • N (tank) endorsement — bulk liquid

     Required for any CMV designed to transport liquid or gaseous materials in a permanently mounted or temporarily attached tank with a rated capacity of 1,000 gallons or more (or any size if the tank is permanently attached). Critical concept: BAFFLE-LESS (or partly baffled) tanks suffer from LIQUID SURGE — the load sloshes forward when the driver brakes, pushing the truck through the intersection. SMOOTH BORE tanks are the worst. To manage: brake EARLIER and SLOWER, never tailgate, and remember the load can shift sideways into curves. Also: do not load above tank capacity (allow for thermal expansion ~2-5%) and never load incompatible products in adjacent compartments without proper purging.

   • H (hazmat) endorsement — TSA background check

     Required to transport placardable quantities of hazardous materials. To get an H endorsement: pass the hazmat written test, AND submit fingerprints + biographic info to TSA under 49 CFR 1572 ("Threat Assessment Standards"). TSA reviews criminal history, immigration status, and intelligence holdings. Disqualifying offenses include certain felony convictions (terrorism, espionage, treason) and misdemeanor convictions for crimes-of-violence within specific look-back windows. Renewal cycles match the CDL itself. On the road: hazmat drivers are subject to additional rules — placarding, route restrictions (tunnels, bridges, urban areas), shipping papers must be within driver's reach, daily logs must specifically note hazmat carriage. Construction relevance: fuel transport (diesel, gasoline) and asphalt distributors at high temperature are both placarded.

     Reference: 49 CFR 1572 (TSA Threat Assessment) + 49 CFR 177 (Hazmat carriage)

   • T (doubles/triples) endorsement

     Required to pull TWO or THREE trailers. The longest trailer goes IMMEDIATELY behind the tractor; the shorter trailer goes in the rear (smaller is more stable when whipping). Couple the heaviest loaded trailer first. Doubles/triples are highly susceptible to "crack-the-whip" amplification — small steering inputs at the tractor become large lateral movements at the rear trailer. Reduce speed in turns and on rolling roads. Many state DOTs limit doubles to specific roadways. The T-endorsement test focuses on coupling/uncoupling sequences, weight distribution, and the math of braking distances for multi-unit combinations.

   Practice questions (2)

   1. 1. A driver is operating a smooth-bore (un-baffled) tank truck loaded with diesel fuel. Compared to a baffled tank, what is the primary additional driving challenge?

      • A.Higher fuel consumption
      • B.Forward liquid surge during braking — load pushes the truck into the intersection✓ correct
      • C.Tighter turning radius
      • D.Reduced top speed by federal rule

      Smooth-bore tanks have no internal baffles to break up liquid motion. When the driver brakes, the entire liquid mass surges FORWARD, then ROCKS BACKWARD — the truck can be pushed through an intersection or rocked dangerously at a stop. Baffled tanks reduce this dramatically. Higher fuel consumption (A) is unrelated. Turning radius (C) is set by the truck geometry, not the bore. Federal rules don't cap top speed by tank type (D).

   2. 2. In addition to passing the hazmat written test, what additional federal requirement must a candidate complete for the H endorsement?

      • A.A road test in a tank truck
      • B.A TSA Threat Assessment under 49 CFR 1572 (fingerprints + background check)✓ correct
      • C.Six months of supervised driving
      • D.A medical certification beyond the standard DOT card

      49 CFR 1572 requires hazmat-endorsement applicants to submit fingerprints and biographic info to TSA, which screens for disqualifying criminal convictions, immigration status, and intelligence holdings. There is no road test SPECIFIC to hazmat (the driver's skills test was for the underlying CDL). Supervised driving is not a federal hazmat requirement. The standard DOT medical card suffices.

External resources

• Official
  FMCSA — Commercial Driver's License Program ↗

  Federal CDL program homepage. Regulatory text (49 CFR Part 383), driver-record requirements, ELDT (Entry-Level Driver Training) rules effective 2022, and disqualification look-up. Start here for federal context, then download YOUR STATE'S CDL Manual for testing specifics.

• Official
  AAMVA Model Commercial Driver's Manual ↗

  AAMVA (American Association of Motor Vehicle Administrators) publishes the model manual most state CDL Manuals are derived from. Identical chapter structure across states. Reading the AAMVA model alongside your state manual reveals the small but important state-specific differences.

• Official
  TSA Hazardous Materials Endorsement Threat Assessment ↗

  TSA portal for the H-endorsement background check. Schedules fingerprinting at IdentoGO sites, posts disqualifying offenses, and explains the renewal/redress process. Apply 60-90 days before you actually need the H — TSA processing is the bottleneck.