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Key Facts: RI CDL Air Brakes Exam

$23.50

Fee for CDL knowledge test

RI DMV Commercial Fees

80%

Minimum passing score

49 CFR 383.135

55-60 psi

Low air warning activation threshold

RI CDL Manual Section 5

20-45 psi

Spring brake automatic pop-out range

49 CFR 393.41

Rhode Island DMV publishes a 25-question CDL Air Brakes knowledge test with 20 correct answers required (80%). Commercial drivers must also demonstrate the applicable air-brake inspection in a full-air-brake vehicle to prevent or remove the L restriction.

Sample RI CDL Air Brakes Practice Questions

Try these sample questions to review concepts for the RI CDL Air Brakes exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 215+ question experience with AI tutoring.

1What are the three distinct braking systems that make up a commercial vehicle air brake system?
A.The service brake, the parking brake, and the emergency brake system
B.The hydraulic brake, the electric brake, and the mechanical drum brake
C.The exhaust brake, the driveline retarder, and the engine jake brake
D.The primary air tank, the secondary air tank, and the auxiliary compressor
Explanation: An air brake system is composed of three separate systems: the service brake system (operated by the foot pedal during normal driving), the parking brake system (used when parked), and the emergency brake system (uses parts of service and parking brakes to stop if air fails).
2What is the function of the air compressor in a commercial vehicle air brake system?
A.It pumps air into the air storage reservoirs (tanks)
B.It cools the brake drums during heavy descending braking
C.It filters moisture out of the diesel fuel injection line
D.It mechanically squeezes the brake shoes against the brake drum
Explanation: The air compressor is connected directly to the vehicle engine (via gears or a V-belt) and pumps atmospheric air under pressure into the storage tanks to operate the air brakes.
3How does the air compressor governor control air pressure in the supply reservoirs?
A.It stops compressor pumping when pressure reaches the cut-out level and resumes pumping when pressure drops to the cut-in level
B.It automatically vents compressed air through the vehicle exhaust pipe when descending hills
C.It varies engine idle speed to maintain exactly 50 psi in all tanks
D.It modulates hydraulic brake fluid pressure between front and rear axles
Explanation: The governor controls when the compressor pumps air. When reservoir pressure reaches the cut-out level (typically between 120 and 140 psi, usually 125 psi), it stops pumping. When pressure drops to cut-in (around 100 psi), it resumes pumping.
4At what typical air pressures should the air compressor governor cut out and cut in?
A.Cut-out between 120 and 140 psi (typically around 125 psi), and cut-in at around 100 psi
B.Cut-out at 60 psi, and cut-in at 45 psi
C.Cut-out at 200 psi, and cut-in at 150 psi
D.Cut-out at 90 psi, and cut-in at 75 psi
Explanation: Under FMCSA and Rhode Island CDL standards, the governor stops compressor pumping (cuts out) between 120 and 140 psi (usually 125 psi) and starts pumping again (cuts in) when pressure falls to approximately 100 psi (minimum 85-100 psi).
5Why must compressed air storage tanks be drained regularly if they are not equipped with automatic drains?
A.Water and compressor lubricating oil collect in tanks, which can freeze in winter causing brake failure and damage valves
B.To prevent excess air pressure from causing the steel tanks to burst at highway speeds
C.To lubricate the brake linings by spraying moisture directly onto the brake drums
D.To lower vehicle gross weight for state weigh-station compliance
Explanation: Compressed air cools as it enters tanks, causing water vapor to condense and mix with compressor oil. If not drained daily, this mixture causes rust, valve sludge, and can freeze in winter lines, causing total brake failure.
6How often should manual air tank drain valves be operated on a commercial vehicle without automatic drains?
A.At the end of each day of driving
B.Once every 30 days during monthly preventive maintenance
C.Only when the low air pressure warning buzzer sounds
D.Only during annual state safety inspection appointments
Explanation: Manual drain valves must be opened at the end of each operating day to purge all accumulated water and compressor oil from the bottom of every air tank.
7In cold-weather service, what job does an air-system alcohol evaporator perform?
A.It introduces alcohol vapor into the air system to prevent moisture from freezing in the brake lines in cold weather
B.It removes oil vapor before compressed air reaches the governor
C.It lowers reservoir pressure whenever outside temperature drops below freezing
D.It replaces the need to drain moisture from air tanks during winter
Explanation: In cold climates, alcohol evaporators introduce alcohol into the compressed air lines, which lowers the freezing point of water condensation and prevents valves and air lines from freezing up in winter.
8What does a safety relief valve in an air brake supply reservoir do, and at what pressure is it set to open?
A.It protects the tank and air lines from excessive pressure and is typically calibrated to open at 150 psi
B.It opens at 60 psi to activate the driver's low-pressure warning light
C.It opens at 100 psi to signal the governor to resume compressor pumping
D.It vents diesel fuel if the fuel pump exceeds 25 psi
Explanation: A safety relief valve is installed in the first (supply) tank to protect the system from overpressurization if the governor malfunctions. It is set to open and vent air automatically at 150 psi.
9What happens when you push down on the brake pedal (foot valve or treadle valve)?
A.Air pressure from the storage tanks is directed through lines to the brake chambers to apply the brakes
B.Hydraulic fluid is forced into the slave cylinder to push against the brake shoes
C.Mechanical cables pull directly on the brake drums to slow the vehicle
D.Compressed air is vented out of the brake chambers, allowing spring brakes to engage
Explanation: Pushing the brake pedal opens the foot valve, allowing compressed air stored in the tanks to flow through control lines into the brake chambers, where it pushes the diaphragm and rod to apply the foundation brakes.
10What is the most common type of foundation brake used on commercial motor vehicles?
A.S-cam drum brakes
B.Electromagnetic retarder brakes
C.Mechanical cable-actuated band brakes
D.External caliper contracting drum brakes
Explanation: S-cam drum brakes are the most common foundation brakes found on commercial vehicles. When air enters the brake chamber, it pushes a rod and slack adjuster, rotating the S-cam to press brake shoes against the drum.

About the RI CDL Air Brakes Exam

The Rhode Island CDL Air Brakes knowledge test is administered by Rhode Island DMV for commercial drivers operating vehicles equipped with air brake systems. It covers Section 5 of the Rhode Island Commercial Driver License Manual, including air-system components, dual systems, inspections, leakage checks, and safe braking. OpenExamPrep provides independent English-language four-option practice for those topics, informed by the manual and federal rules. The official electronic knowledge test uses three-option items, and CDL skills testing includes hands-on air-brake inspection; this bank is not an official translation, format simulation, or substitute for vehicle training.

Exam sponsor: Rhode Island Division of Motor Vehicles (RI DMV). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

A 25-question electronic knowledge test administered by Rhode Island DMV at Cranston headquarters covering Section 5 (Air Brakes) of the Rhode Island Commercial Driver License Manual. Air Brakes is not an endorsement. Passing the knowledge test and demonstrating the required air-brake inspection in a full-air-brake vehicle prevents or removes the L restriction; testing in an air-over-hydraulic vehicle results in a Z restriction.

Time Limit

Not published

Passing Score

80%

Exam / Certification Fees

$23.50 for the initial CDL knowledge test and $10.00 for each additional knowledge test; $73.50 for a new Commercial Learner Permit ($23.50 for an update or duplicate); $103.50 for the CDL skills test.

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

Core Section 5 area

Air Brake System Components

Air compressor, governor cut-in/cut-out, storage tanks, manual and automatic drain valves, alcohol evaporators, and safety relief valves.

Core Section 5 area

Brake Controls and Foundation Brakes

Brake pedal (foot valve), S-cam drum brakes, disc brakes, wedge brakes, slack adjusters, brake pushrods, and brake drums/linings.

Core Section 5 area

Dual Air Systems and Warning Devices

Primary and secondary air systems, supply and application pressure gauges, low air pressure warnings before 55 psi, and spring brake pop-out between 20-45 psi.

Core Section 5 area

Air Brake Inspection and Leakage Tests

Engine-off static leakage check, applied pressure leakage test, low pressure warning check, emergency spring brake check, and compressor build-up timing.

Core Section 5 area

Using Air Brakes and Emergency Procedures

Normal stopping, brake lag distance, controlled braking vs stab braking, steep downgrade braking (snub braking), brake fade, and parking brake use.

Preparing for the RI CDL Air Brakes Exam

What You Need to Know

  • Passing score: 80%
  • Assessment: A 25-question electronic knowledge test administered by Rhode Island DMV at Cranston headquarters covering Section 5 (Air Brakes) of the Rhode Island Commercial Driver License Manual. Air Brakes is not an endorsement. Passing the knowledge test and demonstrating the required air-brake inspection in a full-air-brake vehicle prevents or removes the L restriction; testing in an air-over-hydraulic vehicle results in a Z restriction.
  • Time limit: Not published
  • Exam / certification fees: $23.50 for the initial CDL knowledge test and $10.00 for each additional knowledge test; $73.50 for a new Commercial Learner Permit ($23.50 for an update or duplicate); $103.50 for the CDL skills test. Official sources

Using Our Practice Resources

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RI CDL Air Brakes: Suggested Study Strategy

1Study Section 5 (Air Brakes) of the Rhode Island Commercial Driver License Manual thoroughly.
2Master the 7-step pre-trip air brake inspection and the in-cab air brake tests: governor cut-in (around 100 psi) and cut-out (between 120-140 psi, typically 125 psi), static leakage, applied leakage, low air warning, and spring brake valve pop-out (between 20-45 psi).
3Memorize the maximum pushrod travel for slack adjusters: manual adjusters should not move more than about 1 inch where the pushrod attaches to the slack adjuster.

Frequently Asked Questions

How many questions are on the Rhode Island Air Brakes knowledge test?

The current Rhode Island Commercial Driver License Manual publishes 25 questions. A candidate must answer at least 20 correctly, which is 80%.

What happens if I do not take the Air Brakes test in Rhode Island?

If you do not pass the Air Brakes knowledge test or do not perform the skills test in an air-brake equipped commercial vehicle, Rhode Island DMV will place an L restriction on your CDL, restricting you to vehicles without air brakes.

At what air pressure must the low air warning activate?

Under FMCSA regulations and the Rhode Island Commercial Driver License Manual, the low air pressure warning device (light, buzzer, or wig-wag) must activate before air pressure in either reservoir drops below 55 psi (or 60 psi on many vehicles).

What are the acceptable air leakage rates for commercial vehicles?

With the engine off and brakes released (static), single vehicles must not lose more than 2 psi per minute, and combinations must not lose more than 3 psi per minute. With service brakes fully applied, maximum allowable leakage is 3 psi per minute for single vehicles and 4 psi per minute for combinations.