CDL General Knowledge Practice Test

Updated October 27, 2026

1. You're driving a 40-foot vehicle at 35 mph. According to the CDL manual, how many seconds of following distance should you keep at a minimum?
   A.2 secondsB.4 secondsC.5 secondsD.8 seconds
2. You're stopped on the shoulder of a two-lane road. Where should you place your three reflective warning triangles?
   A.All three within 10 feet behind the vehicleB.One about 10 feet behind, one about 100 feet behind and one about 100 feet ahead of the vehicleC.One at the front, one at the side and one at the backD.Three hundred feet behind the vehicle, all together
3. What is the minimum tread depth for tires on the front (steering) axle?
   A.2/32 inchB.4/32 inchC.6/32 inchD.1/32 inch
4. Your vehicle starts to skid because the drive wheels lost traction on a slippery road. What should you do first?
   A.Brake hardB.Turn the steering wheel sharply the other wayC.Stop braking or accelerating, and steer where you want to goD.Shift to a lower gear and accelerate
5. When is hydroplaning most likely?
   A.When the road is dry and hotB.Only in heavy snowC.When driving slowly on gravelD.When there's standing water, speed is high and tires are underinflated or worn
6. How should you check that your cargo is secure on a trip?
   A.Check it within the first 50 miles, then every 150 miles or every 3 hours, whichever comes first, and after every breakB.Check it only before you leaveC.Check it only if you hear a noiseD.Check it once a day
7. Why is it dangerous to drive with a hot engine and then remove the radiator cap right away?
   A.The engine will stop immediatelyB.The coolant can boil over and scald youC.It drains the batteryD.It is only dangerous in cold weather
8. How far ahead does the CDL manual say most good drivers look?
   A.3 to 5 secondsB.5 to 8 secondsC.12 to 15 secondsD.30 to 40 seconds
9. Total stopping distance is made up of:
   A.Braking distance onlyB.Perception distance, reaction distance and braking distanceC.Reaction distance and tire distanceD.Following distance and braking distance
10. Under federal rules, what blood alcohol concentration is the limit for a driver operating a commercial motor vehicle?
    A.0.02%B.0.04%C.0.08%D.0.10%
11. When driving at night, when should you switch to low beams?
    A.Only in citiesB.Never on highwaysC.When an oncoming vehicle is within about 500 feet, or when following a vehicle within about 500 feetD.Within 50 feet of another vehicle
12. You're going down a long, steep downgrade. When should you shift to a lower gear?
    A.Halfway down the hillB.At the bottom of the hillC.Only if the brakes start to fadeD.Before starting down the grade
13. Using the snub braking method on a downgrade, when do you release the brakes?
    A.When speed is about 5 mph below your safe speedB.When the vehicle stops completelyC.When the brakes start to smellD.When the engine stalls
14. How many tiedowns does cargo need, at a minimum, under the model CDL manual?
    A.One tiedown for every 20 feet, minimum oneB.One tiedown for every 10 feet of cargo, and at least two tiedowns no matter how small the cargoC.Two tiedowns for every 5 feetD.Tiedowns are optional for cargo under 1,000 pounds
15. What type of fire is a B:C extinguisher designed for?
    A.Wood and paper fires onlyB.Metal firesC.Flammable liquid and electrical firesD.Tire fires only
16. When backing a large vehicle, which way should you back when possible?
    A.Toward the passenger sideB.Straight back without lookingC.DownhillD.Toward the driver's side