CDL General Knowledge Practice Test (2026)

CDL General Knowledge Practice Test is a focused set of exam-style questions for 2026 with a “Show Answer” toggle for review. Each item includes the correct answer, a short explanation, and official citations so you can confirm the rule in the handbook. Work in full runs, mark what you miss, then retake those rule types until the decisions feel automatic.

FAQ

What is on a CDL general knowledge practice test?

Expect rules-based items on inspection basics, safe driving, speed and space management, hazard recognition, and air‑brake awareness at a high level. The goal is applying handbook rules to short scenarios, not memorizing definitions.

How should I use CDL general knowledge practice questions?

Answer first, then open “Show Answer” to read the explanation and verify the cited rule. Track the concepts you miss (space, hazards, inspection) and retake those topics later until you can apply the rule in new wording.

Is there a CDL general knowledge practice test PDF option?

PDF sets are useful for printing or offline review, but the best study method is still active recall: attempt each item, then check the explanation and citation. If you print, cover the answers and work in timed passes.

Where can I take a free CDL general knowledge practice test?

Use a full run to find weak areas, then do focused retakes on the same rule type (following distance, braking, inspection order). Don’t skim answers first—use them only after you commit to a choice.

What questions are on the CDL general knowledge test?

Most questions test how drivers apply safety rules: stopping and following distances, speed control, hazard response, inspections, and basic regulations. This page mirrors the way those rules show up in exam-style wording.

CDL General Knowledge Practice Test

Q1: When inspecting a commercial vehicle before a long trip, which combination of emergency equipment is mandatory under FMCSA and federal regulations?

Q2: In early morning high-humidity conditions, what is the most reliable sign that black ice may have formed on a rural two-lane highway?

Q3: What is the most effective technique to control speed when descending a steep grade with a heavy load to avoid brake fade?

Q4: Under optimal driving conditions, how far ahead should a CDL driver scan the roadway to safely anticipate changes?

Q5: Which best defines ‘reaction distance’ for a combined tractor-trailer vehicle traveling at highway speed?

Q6: At 65 mph, what minimum following distance should a CDL driver maintain under dry conditions using the three-second rule?

Q7: When negotiating a sharp curve on a two-lane highway, what adjustment helps prevent rollover in a high center-of-gravity vehicle?

Q8: During a pre-trip inspection, how should a driver determine if recap tires are within service limits?

Q9: What is the safest procedure when driving through dense fog at night in an open rural area?

Q10: Why is it important to avoid ‘riding’ the brakes on vehicles with drum brakes during extended descents?

Q11: Which formula correctly estimates stopping distance at highway speeds for a fully loaded truck?

Q12: How should cargo be distributed on tandem axles to comply with federal weight regulations?

Q13: Under federal hours-of-service rules, after how many cumulative hours of driving is a 30-minute break required?

Q14: When transporting loose logs or lumber, what securement device is REQUIRED by FMCSA?

Q15: How does high-altitude driving above 5,000 feet affect a diesel engine’s performance?

Q16: What is the correct procedure when crossing railroad tracks with reducible force warning devices?

Q17: Which step is essential when coupling a tractor to a semi-trailer?

Q18: How should you test for hydraulic brake system leaks during pre-trip inspection?

Q19: If your vehicle’s lights fail at night, which hand signal indicates a left turn?

Q20: What distinguishes interstate commercial vehicles from intrastate vehicles?

Q21: At a railroad crossing with non-functioning warning signals, what must a CDL driver do?

Q22: What is the maximum legal weight for a tandem axle group ? CDL regulations?

Q23: Which technique helps prevent jackknifing when making a sharp right turn with a tractor-trailer?

Q24: What is the correct method for checking engine coolant levels in a heavy-duty diesel before driving?

Q25: Calculate the total stopping distance for a truck traveling at 55 mph if reaction time is 2 seconds and braking distance is 200 feet.

Q26: What is the primary purpose of adjusting your side mirrors before driving a tractor-trailer?

Q27: If the oil temperature gauge shows a rapidly rising temperature, what is the safest immediate action?

Q28: During pre-trip inspection, you notice coolant dripping under the radiator. What does this indicate?

Q28: When driving down a steep grade in mountainous terrain, what pattern of braking is recommended?

Q30: Which device helps slow a heavy vehicle without using service brakes, reducing brake wear?

Q31: What is the maximum low air pressure allowance for air brake leakage during a one-minute static test?

Q32: How do spring brakes activate in an air brake system?

Q33: How is the static air brake leakage test properly performed?

Q34: During the slack adjuster check, what indicates the adjuster is out of adjustment?

Q35: Why is fatigue considered as dangerous as alcohol impairment for CDL drivers?

Q36: If you must pull onto the shoulder to inspect a mechanical issue, what is the proper safety procedure?

Q37: What is the required minimum number of warning devices around a stopped commercial vehicle on a two-lane highway?

Q38: Which placard is required when hauling corrosive materials classified under Hazard Class 8?

Q39: When passing a slow-moving vehicle on a narrow two-lane road, what action ensures safety?

Q40: At what distance should you begin to dim your headlights when approaching another vehicle at night?

Q41: Which behavior is considered a major distraction for a CDL driver while operating the vehicle?

Q42: What is the recommended action when approaching a drawbridge that is about to open?

Q43: Chevron road signs on sharp curves indicate:

Q44: Why must a fire extinguisher be easily accessible and not stored under a seat or behind cargo?

Q45: How does prolonged driving at high speeds affect tire temperature and safety?

Q46: If the front axle is overloaded, what steering issue is most likely to occur?

Q47: Why should high beams be dimmed when following another vehicle at night?

Q48: When should the emergency air line be used in combination vehicle braking?

Q49: What does the ABS malfunction lamp indicate on a commercial vehicle dash?

Q50: During coupling inspection, how far should the fifth wheel be tilted before backing under the trailer?

Q51: Which placard is required when transporting infectious substances under DOT classification 6.2?

Q52: When performing a straight-line backing maneuver, what steering technique is recommended?

Q53: Under federal regulations, how often must a commercial driver inspect the vehicle’s lights during a trip?

Q54: What is the maximum legal width for most commercial vehicles ?, excluding certain over-width permits?

Q55: To prevent cargo shift, what is the minimum angle for binders when securing logs or poles?

Q56: When merging onto a highway from an acceleration lane, what speed should you aim for before merging?

Q57: During a CDL road test, which action demonstrates proper understanding of a dual air brake system?

Q58: What is the primary cause of brake fade during continuous braking on long downgrades?

Q59: Which log entry is mandatory at the start of a driver’s day?

Q60: What describes the proper technique for ‘snub braking’ on a steep downgrade?

Q61: Under FMCSA hours-of-service rules, what is the maximum on-duty period in a 14-hour window?

Q62: Which indicator light warns of low air pressure in an air brake system?

Q63: What is the safest method to check clearance under a loaded flatbed trailer?

Q64: Which pre-trip check ensures spring brakes will engage if air pressure is lost?

Q65: When transporting liquid bulk, what factor most affects stopping distance?

Q66: What is the correct procedure for verifying the operation of tractor protection valve?

Q67: In which situation is hydroplaning most likely to occur?

Q68: During pre-trip inspection, what method is used to check suspension components for damage?

Q69: Which document must always be present when hauling regulated hazardous materials?

Q70: When making a lane change on a multi-lane highway, what is the minimum mirror check sequence?

Q71: What does a yellow diamond-shaped sign with a semi-truck tipping icon warn drivers of?

Q72: Which factor most affects air brake lag distance?

Q73: What is the purpose of the governor in an air brake system?

Q74: Which condition requires a driver to report a tire pressure issue immediately?

Q75: How is the anti-lock braking system (ABS) checked during a pre-trip inspection?

Q76: What is the correct minimum tread depth for front steering axle tires under FMCSA regulations?

Q77: How often must a CDL driver record a change of duty status that lasts longer than 15 minutes?

Q78: During pre-trip inspection, which sign of hydraulic fluid leak is unacceptable?

Q79: What is the maximum blood alcohol concentration (BAC) allowed for CDL drivers under federal law?

Q80: Which method helps prevent tail swing accidents when turning a tractor-trailer?

Q81: How should a driver verify the functionality of the parking brake in an air brake system?

Q82: What is the primary reason for waiting two minutes after turning off the engine before checking valve lash on a diesel engine?

Q83: Which condition indicates antilock braking system (ABS) is active during stopping?

Q84: When transporting livestock, what feature is essential for proper ventilation?

Q85: Under federal law, what is the minimum number of reflective devices required on the rear of a commercial motor vehicle operating at night?

Q86: What technique helps reduce trailer fishtailing during gusty wind conditions?

Q87: Which log entry must a driver make immediately after loading hazardous materials?

Q88: What identifies the service and emergency air lines on a combination vehicle?

Q89: What action should a driver take if a tire pressure monitoring system (TPMS) warns of a low-pressure tire?

Q90: Which FMCSA regulation governs the transport of refrigerated food products?

Q91: How should you position warning devices when stopped on a two-way, two-lane road at night?

Q92: Which factor determines the required length of a pre-trip inspection report under FMCSA?

Q93: What’s the main purpose of an anti-lock braking system in commercial vehicles?

Q94: What is the legal limit for axle weight on single axles ? without special permits?

Q95: How is snub braking properly applied during a long downhill descent?

Q96: Which record must a driver keep for 6 months as per FMCSA regulations?

Q97: When is it permissible to cross a double solid yellow centerline?

Q98: What must be checked regarding the fifth wheel during coupling on a slippery surface?

Q99: Which hazard class requires placarding on all four sides of the vehicle?

Q100: How much distance does a tractor-trailer travel during perception time at 55 mph if perception time is 1.5 seconds?

Related practice options:

CDL General Knowledge Practice Tests (By State) (2026)
Florida 2026 CDL Class A General Knowledge Test (HTML)
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