2026 CDL General Knowledge Practice Test

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?

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