CDL Combination Exam Sample Test: Ready to Ace It?
Test your knowledge on air leakage rates and doubles handling - dive in!
This free quiz helps you prep for the CDL Combination Exam by practicing air leakage rates, pulling doubles, coupling and uncoupling, and pre-trip checks. Use it to spot weak areas before test day, and if you want more, try our CDL practice mix or review brakes with the air brake quiz .
Study Outcomes
- Understand Air Leakage Rate for Combination Vehicles -
Identify the maximum allowable air leakage rate for a combination vehicle to maintain safe braking performance, a critical requirement for the CDL combination exam.
- Apply Safe Doubles Handling Techniques -
Demonstrate proper control methods and preventive measures when you turn suddenly while pulling doubles, ensuring vehicle stability and cargo safety.
- Recall Essential Pre-Trip Inspection Steps -
Review and list key inspection points for cdl combination vehicles, enabling early detection of mechanical issues before highway operation.
- Analyze Combination Vehicle Test Answers -
Dissect common question formats and answer choices to accurately select the correct responses on the combination vehicle portion of the cdl combination exam.
- Evaluate Risk Situations -
Assess real-world driving scenarios involving combination vehicles to recognize hazards such as trailer sway and jackknife potential, and apply appropriate corrective actions.
Cheat Sheet
- Air Leakage Rate Standards -
According to FMCSA Part 393 regulations, a combination vehicle must not exceed an air loss of 3 psi per minute with the engine off during a one-minute static hold. For example, if the system reads 90 psi, it should not drop below 87 psi after one minute - remember "Three per minute for combination."
- Coupling and Uncoupling Procedures -
Follow the North American Standardized Coupling Procedure: inspect fifth wheel jaw engagement, ensure kingpin is locked, and verify release arm is secure. Use the mnemonic "Lock, Lube, Level" to confirm jaws are closed, plate is greased, and trailer is level before driving.
- Handling Doubles in Turns -
When you turn suddenly while pulling doubles, trailers can "cut in" and increase off-tracking; start the turn wider and maintain a steady speed to keep both trailers aligned. University of Minnesota research recommends a "Lead-Lag-Lead" steering approach: lead with tractor, lag second trailer, then align on exit.
- Weight Distribution and Balance -
Use calibrated scales to ensure no axle group exceeds its Gross Axle Weight Rating (GAWR) and that the Center of Gravity stays within manufacturer limits. A quick formula: GCWR ≥ (Truck Weight + Trailer Weight + Cargo Weight) to avoid overloading penalties and maintain stability.
- Brake System Inspection -
Refer to the CVSA Brake Inspector's Manual for a comprehensive pre-trip: test trailer air leak-down rate, verify tractor protection valve activation, and confirm emergency brakes hold at 20 - 40 psi in the trailer tank. Always listen for air leaks near glad hands and inspect airlines for kinks or abrasions.