CDL Air Brake Brake Fade and Downgrade Driving 2 — Questions and Answers
Question 1: Before descending a steep grade, where should you check your brakes?
- At the bottom of the grade after the descent
- At the top of the grade before beginning the descent (Correct answer)
- Halfway down the grade when speed builds up
- Brake checks are not required before a descent
Correct answer: At the top of the grade before beginning the descent
Always check your brakes at the top of a steep grade before beginning the descent to ensure they are functioning properly.
Question 2: What role does the transmission play in controlling speed on long downgrades?
- The transmission has no effect on downgrade speed control
- Higher gears provide more engine braking than lower gears
- Lower gears provide greater engine braking to help control speed (Correct answer)
- Automatic transmissions cannot assist with downgrade speed control
Correct answer: Lower gears provide greater engine braking to help control speed
Lower gears provide greater engine braking because the engine works against higher compression, helping slow the vehicle without relying on service brakes.
Question 3: What is a runaway truck ramp designed for?
- A rest stop for trucks on steep grades
- An emergency escape route for vehicles that have lost braking ability on a descent (Correct answer)
- A weigh station for overweight vehicles
- A turnaround point for trucks that missed their exit
Correct answer: An emergency escape route for vehicles that have lost braking ability on a descent
Runaway truck ramps provide an emergency escape route filled with gravel or sand that stops vehicles that have lost brake effectiveness on a downgrade.
Question 4: What happens to brake drums as they heat up during prolonged braking?
- They shrink and grip the brake shoes more tightly
- They expand, which can reduce contact with brake shoes and lessen braking force (Correct answer)
- They remain the same size regardless of temperature
- They soften and provide better friction
Correct answer: They expand, which can reduce contact with brake shoes and lessen braking force
Brake drums expand when heated, which can reduce contact with brake shoes, contributing to brake fade and reduced stopping power.
Question 5: Why should you NOT use brakes continuously to hold a constant speed on a long downgrade?
- It wears out brake pads faster than any other driving behavior
- It significantly increases fuel consumption on the descent
- Continuous application causes heat buildup that leads to brake fade (Correct answer)
- It is illegal in most states to hold constant brake pressure
Correct answer: Continuous application causes heat buildup that leads to brake fade
Continuous brake application generates excessive heat that causes brake fade, making the brakes ineffective when you need them most.
Question 6: What material are runaway truck ramp arrestor beds typically filled with?
- Water or foam to absorb impact
- Loose sand or pea gravel that creates resistance to stop runaway vehicles (Correct answer)
- Rubber padding for cushioned stopping
- Steel cables to catch the vehicle
Correct answer: Loose sand or pea gravel that creates resistance to stop runaway vehicles
Runaway truck ramps are typically filled with loose sand or pea gravel that creates drag resistance to safely stop an out-of-control vehicle.
CDL Air Brake Brake Fade and Downgrade Driving 2
Before descending a steep grade, where should you check your brakes?