CDL General Knowledge Practice Test — Questions and Answers
Question 1: What is the minimum following distance recommended for a commercial motor vehicle under normal conditions at highway speeds?
- One second for every 10 feet of vehicle length (Correct answer)
- 2 car lengths regardless of speed
- Three seconds regardless of vehicle length
- 50 feet at all speeds
Correct answer: One second for every 10 feet of vehicle length
For speeds above 40 mph, CMV drivers should maintain at least one second of following distance per 10 feet of vehicle length. For a 60-foot vehicle at highway speed, that's at least 6 seconds. In adverse conditions (rain, snow, night), this should be doubled.
Question 2: Under FMCSA regulations, a CMV driver may drive a maximum of how many hours after 10 consecutive hours off duty (property-carrying vehicles)?
- 11 hours (Correct answer)
- 10 hours
- 8 hours
- 14 hours
Correct answer: 11 hours
Under the FMCSA Hours of Service rules for property-carrying drivers, a driver may drive a maximum of 11 hours after taking 10 consecutive hours off duty. Additionally, the driver cannot drive beyond the 14th hour after coming on duty, regardless of how many hours were actually driven.
Question 3: What does a diamond-shaped sign with a yellow background typically indicate?
- A warning about upcoming road conditions (Correct answer)
- A regulatory requirement that must be obeyed
- A service or guide to nearby facilities
- A construction zone speed limit
Correct answer: A warning about upcoming road conditions
Diamond-shaped signs with yellow backgrounds are warning signs in the US highway sign system. They alert drivers to upcoming conditions that may require speed adjustments or extra caution, such as curves, intersections, pedestrian crossings, or construction zones.
Question 4: When are you required to inspect your cargo during a trip?
- Within 50 miles after starting, then every 3 hours or 150 miles (Correct answer)
- Only at the start and end of each trip
- Once every 24 hours
- Only if the load exceeds 10,000 lbs
Correct answer: Within 50 miles after starting, then every 3 hours or 150 miles
FMCSA regulations require cargo inspections within the first 50 miles after loading, and then at every 3 hours or 150 miles of driving, whichever comes first. Drivers must also inspect cargo after any change in duty status. This applies to loads that could shift or become unsecured.
Question 5: What is the primary reason large trucks take longer to stop than cars at the same speed?
- Greater mass means more kinetic energy that must be overcome by braking (Correct answer)
- Truck brake systems are less efficient than car brakes
- Trucks have fewer brake pads than cars
- Air brakes respond more slowly than hydraulic brakes in all conditions
Correct answer: Greater mass means more kinetic energy that must be overcome by braking
The primary reason is the much greater mass (kinetic energy) of a loaded truck. A fully loaded semi can weigh up to 80,000 lbs compared to ~4,000 lbs for a car — 20 times more mass. Kinetic energy increases with the square of speed AND linearly with mass, so stopping distance is dramatically greater.
Question 6: What should you do if you become drowsy while driving a commercial vehicle?
- Pull off the road safely and sleep until you are rested (Correct answer)
- Open the window and drink coffee to stay alert
- Turn up the radio and continue to the next rest stop
- Increase speed to reach your destination faster
Correct answer: Pull off the road safely and sleep until you are rested
If drowsiness occurs, the only safe action is to stop and rest. Drowsiness is a critical safety hazard — studies show that drowsy driving impairs reaction time as severely as drunk driving. Opening windows, turning up the radio, or drinking coffee are not reliable remedies and can create a false sense of security.
CDL General Knowledge Practice Test
What is the minimum following distance recommended for a commercial motor vehicle under normal conditions at highway speeds?