CDL Combination Vehicles Test practice questions
205 free questions with answers and explanations.
- 101.A combination vehicle has an air leak in the emergency (supply) air line between the tractor and the trailer. What will be the primary effect on the trailer's braking system if this leak occurs while driving?Combination Vehicle Air Brakes
- 102.A driver of a combination vehicle is preparing to enter a curve on a rural highway. The posted speed limit for the straightaway leading to the curve is 65 mph. The driver observes a warning sign indicating a recommended curve speed of 35 mph. What is the most crucial action the driver should take before entering the curve?Driving Combination Vehicles Safely
- 103.A commercial driver is operating a combination vehicle and observes a large, unsecured object fall off a flatbed truck several hundred feet ahead in their lane. What is the safest and most effective defensive driving technique for the driver to employ?Driving Combination Vehicles Safely
- 104.During a pre-trip inspection of a combination vehicle, a driver finds that the fifth wheel locking jaws are not fully closed around the kingpin. What is the immediate and most critical action the driver should take?Driving Combination Vehicles Safely
- 105.When driving a combination vehicle, which factor is most likely to increase the risk of rollovers?Driving Combination Vehicles Safely
- 106.When inspecting a combination vehicle's air brake system, you discover that the slack adjusters on several brake chambers move more than one inch when pulled by hand. What is the correct course of action?Combination Vehicle Air Brakes
- 107.When driving a combination vehicle, how does a sudden, hard application of the service brakes on a slippery surface typically affect the trailer?Driving Combination Vehicles Safely
- 108.A commercial driver is operating a combination vehicle on a downhill grade during a rainstorm. The driver notices the rear of the trailer beginning to sway from side to side. What is the most appropriate immediate action to take?Driving Combination Vehicles Safely
- 109.A driver is performing a pre-trip inspection of a combination vehicle. They check the trailer's wheel ends and notice a small amount of oil leaking from the hub seal of one of the wheels. What is the most appropriate action to take?Inspecting Combination Vehicles
- 110.When inspecting the coupling of a combination vehicle, a driver notices that the fifth wheel locking jaws are open. What is the immediate safety concern?Inspecting Combination Vehicles
- 111.When driving a combination vehicle, how often should you check your mirrors to maintain situational awareness and detect potential hazards?Driving Combination Vehicles Safely
- 112.You are driving a combination vehicle and notice that the air pressure gauge for the trailer's service brakes is significantly lower than the tractor's. What does this discrepancy most likely indicate?Driving Combination Vehicles Safely
- 113.A commercial driver is operating a combination vehicle on a level road and observes a pedestrian unexpectedly enter the roadway ahead. What is the most effective braking technique to use to maintain control and stop safely?Driving Combination Vehicles Safely
- 114.A commercial driver is operating a combination vehicle on a two-lane highway. The driver needs to pass a slower vehicle. What is the most critical consideration before initiating the passing maneuver?Driving Combination Vehicles Safely
- 115.A commercial driver operating a combination vehicle is approaching a construction zone with reduced speed limits and narrow lanes. What is the most crucial action to take to ensure safety?Driving Combination Vehicles Safely
- 116.During your pre-trip inspection, you notice that the trailer's landing gear crank handle is bent and difficult to operate, although the landing gear itself appears to be fully retracted. What is the most appropriate action before starting your trip?Inspecting Combination Vehicles
- 117.A commercial driver is operating a combination vehicle and encounters dense fog, significantly reducing visibility to less than 100 feet. What is the safest and most appropriate action the driver should take?Driving Combination Vehicles Safely
- 118.A commercial driver operating a combination vehicle is traveling on a highway at night. The driver notices the high beams of an oncoming vehicle are extremely bright and causing temporary blindness. What is the most effective defensive driving action to take?Driving Combination Vehicles Safely
- 119.A commercial driver is operating a combination vehicle on a level road. The driver needs to make an emergency stop. The vehicle is equipped with an Anti-lock Braking System (ABS). What is the correct technique for emergency braking with ABS?Driving Combination Vehicles Safely
- 120.A commercial driver is planning a trip with a combination vehicle that will involve traveling through mountainous terrain. The vehicle's Gross Combination Weight (GCW) is 70,000 lbs. The driver needs to determine the appropriate safe following distance on a dry road at 50 MPH. Using the rule of thumb for following distance, what should the minimum following distance be?Driving Combination Vehicles Safely
- 121.A commercial driver is operating a combination vehicle and notices that the trailer is swaying excessively from side to side. The road is dry, and there's no strong crosswind. What is the most probable cause of this trailer sway?Driving Combination Vehicles Safely
- 122.During a pre-trip inspection, a driver observes that the air compressor drive belt is frayed and has several cracks. What is the most appropriate action?Combination Vehicle Air Brakes
- 123.A driver is inspecting the glad hands on a tractor-trailer. Which of the following conditions would indicate a problem that needs to be addressed before driving?Combination Vehicle Air Brakes
- 124.A commercial driver is operating a combination vehicle and approaches a section of road where patches of ice are visible. What is the most effective way to maintain control and prevent a skid in this situation?Driving Combination Vehicles Safely
- 125.When driving a combination vehicle, you notice that your trailer is starting to swing wide on a curve. What is the most appropriate immediate action to take?Driving Combination Vehicles Safely
- 126.During a pre-trip inspection of a combination vehicle, you are checking the brake adjustment. The pushrod on a cam-type brake with a 6-inch brake chamber moves 1.5 inches when the brakes are applied. What does this indicate?Inspecting Combination Vehicles
- 127.A driver notices that the air pressure gauge on their combination vehicle is reading 0 psi for the service brake system, but the parking brakes are still released, and the vehicle is moving. What component is most likely failing to engage the parking brakes?Combination Vehicle Air Brakes
- 128.A commercial driver is operating a combination vehicle on a four-lane highway and plans to exit using an off-ramp that curves sharply to the right. To safely navigate this exit, what should the driver do?Driving Combination Vehicles Safely
- 129.A commercial driver operating a combination vehicle notices that the trailer brakes are locking up frequently during light braking, while the tractor brakes are functioning normally. What is the most likely cause of this issue?Driving Combination Vehicles Safely
- 130.You are driving a tractor-trailer and notice your air pressure gauge is showing 70 psi. The low air pressure warning light has just activated. What is the most immediate and critical action you should take?Combination Vehicle Air Brakes
- 131.While driving a combination vehicle, a driver experiences a sudden loss of steering control (e.g., steering wheel spins freely). What is the most critical immediate action the driver should take?Driving Combination Vehicles Safely
- 132.During a pre-trip inspection, you observe that the red (emergency) air line glad hand on your tractor is missing its rubber seal. The blue (service) line glad hand has its seal intact. What is the immediate and most appropriate action?Inspecting Combination Vehicles
- 133.A commercial driver is preparing to descend a long, steep grade with a fully loaded combination vehicle. The driver has downshifted and is using engine braking. What is the maximum safe speed for this descent?Driving Combination Vehicles Safely
- 134.During an en route inspection, you notice that the trailer's brake lights are not illuminating when the service brake pedal is pressed in the tractor. The turn signals and running lights are working correctly. What is the most likely cause of this specific issue?Inspecting Combination Vehicles
- 135.When driving a combination vehicle, how does a sudden change in speed or direction affect the forces acting on the cargo in the trailer?Driving Combination Vehicles Safely
- 136.A commercial driver is operating a combination vehicle and notices that the vehicle ahead has stopped suddenly. To avoid a rear-end collision, what is the best technique for braking a combination vehicle?Driving Combination Vehicles Safely
- 137.You are driving a combination vehicle and experience a sudden tire blowout on one of your trailer tires. What is the immediate and safest action to take?Driving Combination Vehicles Safely
- 138.A driver is performing a functional check of the trailer spring brakes on a combination vehicle. After charging the trailer air system, the driver pushes in the trailer air supply (red) knob and then pulls it out. What should happen when the red knob is pulled out?Combination Vehicle Air Brakes
- 139.You are performing a pre-trip inspection on a combination vehicle's air brake system. After building up full air pressure (120 psi), you shut off the engine, release the parking brake, and fully apply the foot brake. You observe the air pressure gauge. What is the maximum allowable air loss rate for a combination vehicle with the engine off and brakes applied?Combination Vehicle Air Brakes
- 140.When inspecting the air lines on a combination vehicle, a driver finds that the service (blue) air line on the trailer has a significant leak. What is the most immediate and critical consequence of this specific leak?Combination Vehicle Air Brakes
- 141.When inspecting the cargo in a combination vehicle before a trip, you notice that the cargo in the rear of the trailer is not secured tightly against the front bulkhead and appears to have shifted slightly during previous movements. What is the primary concern and required action?Inspecting Combination Vehicles
- 142.What is the function of a 'check valve' located between the primary and secondary air supply tanks in a dual air brake system?Combination Vehicle Air Brakes
- 143.A commercial driver is operating a combination vehicle on a wet road and needs to make an emergency stop. The vehicle is equipped with ABS. What is the correct braking technique?Driving Combination Vehicles Safely
- 144.Which component in a combination vehicle's air brake system is responsible for protecting the air tanks and other components from excessive air pressure by releasing air when it exceeds a safe operating limit?Combination Vehicle Air Brakes
- 145.You are driving a combination vehicle on a highway and notice that a small car has merged in front of you, leaving very little space. What is the most appropriate action to take?Driving Combination Vehicles Safely
- 146.A commercial driver operating a combination vehicle is approaching a sharp curve on a rural highway. The posted speed limit for the highway is 55 MPH, but there is a warning sign indicating a recommended speed of 30 MPH for the curve. To safely navigate this curve, what is the best course of action?Driving Combination Vehicles Safely
- 147.During a pre-trip inspection of a combination vehicle, you notice that the air pressure gauge shows 60 psi, and the low air pressure warning light and buzzer are active. What action should you take?Combination Vehicle Air Brakes
- 148.What is the primary purpose of the 'dummy couplers' or 'dummy glad hands' found on a tractor or trailer?Coupling and Uncoupling
- 149.After successfully coupling a tractor and trailer, and completing all visual checks, a driver observes that the fifth wheel release arm is not fully seated in its locked position, despite the jaws appearing to be around the kingpin. What is the most appropriate action?Coupling and Uncoupling
- 150.A driver is inspecting the kingpin for wear. According to safety regulations, what type of damage or wear on the kingpin would immediately render the trailer unsafe to operate?Coupling and Uncoupling