The air-system safety relief valve is venting because pressure is excessive. How should the driver treat this finding?
Correct answer: As a fault requiring mechanical attention.
The relief valve protects against excessive pressure; it is not the normal pressure-regulating control. A venting safety valve requires investigation and repair, not disabling.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.1.6, physical PDF page 93, printed page 5-2. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
A driver repeatedly presses and releases the air-brake pedal for no reason while waiting to depart. What can happen?
Correct answer: Air may be used faster than the compressor replaces it.
Brake releases discharge air, and the compressor must replenish it. Unnecessary repeated applications can deplete the available supply.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.1.7, physical PDF page 93, printed page 5-2. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
In an S-cam drum brake, what is the purpose of the rotating cam at the wheel?
Correct answer: To press the brake shoes outward against the drum.
The S-cam translates linkage movement into shoe contact with the drum. Friction at that contact slows the wheel; the governor and reservoir have different jobs.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.1.8, physical PDF page 93, printed page 5-2. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
One gauge shows reservoir pressure; an optional second type rises with pedal force. What does that second type indicate?
Correct answer: Pressure being applied to the brakes.
Supply pressure and application pressure are different measurements. An application gauge indicates the pressure used for braking, not the amount stored in the tanks.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.1.9–5.1.10 (supply gauge begins on physical page 93), physical PDF page 94, printed page 5-3. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
A truck has two air-brake circuits but one foot pedal. What does the dual arrangement provide?
Correct answer: Separate air supplies and circuits operated by common controls.
Dual systems separate the air circuits while sharing the driver's controls. Each circuit has its own supply and related components; both must be monitored.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.2, physical PDF page 96, printed page 5-5. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
Using the manual's minimum-pressure guidance for a dual system, one circuit has reached 110 psi but the other is still at 80 psi. Is the truck ready to move?
Correct answer: No; both circuits need at least 100 psi under that guidance.
The cited guidance requires at least 100 psi in both circuits before driving. A healthy reading in one circuit does not substitute for adequate pressure in the other.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.2, physical PDF page 96, printed page 5-5. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
During a trip, one air circuit loses pressure while the other remains charged. What is the appropriate response?
Correct answer: Stop safely and have the air-brake defect corrected.
A dual system may retain enough braking for a controlled stop, but the loss reduces braking capability. The remaining circuit is not permission to continue normal operation.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.2, physical PDF page 96, printed page 5-5. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
An automatic slack adjuster repeatedly shows excessive stroke. What does routinely tightening it by hand fail to address?
Correct answer: The underlying installation, adjuster or brake-component problem.
Repeated manual correction can conceal a defect instead of fixing it. Automatic adjusters still need inspection, and an out-of-adjustment condition needs qualified diagnosis.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.2, physical PDF page 97, printed page 5-6. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
The truck's ABS lamp comes on during travel, but there is no separate loss of conventional braking. What does this indicate?
Correct answer: ABS assistance may be impaired even though regular brakes remain.
An ABS fault does not by itself mean total service-brake failure. Report the fault and obtain service promptly; do not interpret the lamp as normal ABS intervention.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.4.2, physical PDF page 99, printed page 5-8. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
A motorcoach with functioning ABS is making an urgent stop on a slippery road and the ABS begins cycling. How should the driver use the pedal?
Correct answer: Maintain the needed steady application and let ABS regulate pressure.
With functioning motorcoach ABS, repeatedly pumping the pedal interferes with the intended control. Maintain the appropriate application and let the system manage impending wheel lock.
Source: FMCSA Motorcoach Brake Systems and Safety Technologies, Important Points about ABS and Related Technologies; functioning motorcoach ABS pedal technique. ↗
Only the tractor has ABS, and the non-ABS trailer starts swinging during braking. What does the manual advise if it can be done safely?
Correct answer: Ease off the brakes enough to regain control.
ABS on the tractor does not guarantee that the trailer's wheels cannot lock. Monitor the whole combination and reduce braking as needed, when safe, to regain control.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.4.2, physical PDF page 99, printed page 5-8. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
On a long descent, a driver keeps applying the service brakes until they become excessively hot. Why can braking weaken?
Correct answer: Heat can reduce friction and expand the brake drums.
Prolonged brake overuse can reduce effective friction and increase the movement needed to contact an expanded drum. More pedal force is not a reliable cure for overheating.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.4.5, physical PDF page 100, printed page 5-9. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
In the manual's unapplied leak check, a safely chocked single truck has its engine off and parking brake released. Its pressure falls 3 psi in one minute without a foot-brake application. How should that result be assessed?
Correct answer: It exceeds the manual's less-than-2-psi guidance for this single-vehicle check.
Applied and unapplied checks use different criteria. Section 5.3.3 describes less than 2 psi per minute for a single vehicle in this unapplied check; a 3-psi loss needs correction before operation.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.3, Test Air Leakage Rate: unapplied, physical PDF page 97, printed page 5-6. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
When checking the compressor governor on a truck, which pressure should be used to judge whether its cutoff is correct?
Correct answer: The cutoff specified by that vehicle's manufacturer.
The manual gives approximate governor values but directs the driver to the manufacturer's specifications. The safety-relief setting and low-air warning are different checks, not substitutes for the correct governor setting.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.3, Check Air Compressor Governor Cut-in and Cut-out Pressures, physical PDF page 97, printed page 5-6. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
A supervised applied-leak check begins with full air pressure, wheel chocks, and the parking brakes released. Which action prevents compressor output from concealing leakage while the foot brake is held?
Correct answer: Shut off the engine before the timed brake application.
The engine is shut off for the manual's applied-leak check, and the foot brake is fully applied and held. Running the compressor could replace lost air and obscure the condition being checked. Secure the vehicle before releasing parking brakes.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.3, Test Air Leakage Rate: applied, physical PDF page 98, printed page 5-7. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
A safely secured single air-braked truck loses 4 psi during the one-minute held-foot-brake leak check, with the engine off. How does that compare with section 5.3.3's applied-check limit?
Correct answer: It exceeds the 3-psi limit for that single vehicle.
The manual treats more than 3 psi in one minute as excessive in this single-vehicle applied check. A 4-psi loss exceeds it; do not substitute the combination limit or an unapplied-check criterion.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.3, Test Air Leakage Rate: applied single vehicle, physical PDF page 98, printed page 5-7. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
For the standard dual-system example in the manual, with the engine at operating rpm and without oversized-reservoir exceptions, what is the buildup benchmark?
Correct answer: 85 to 100 psi within 45 seconds.
The manual's standard dual-system benchmark is 85–100 psi in 45 seconds. Larger-than-minimum reservoirs may have a different safe buildup time; consult the manufacturer.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.3, physical PDF page 98, printed page 5-7. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
The air system cannot build pressure at the rate specified for that truck. What is the appropriate decision?
Correct answer: Do not drive until the cause is corrected.
Inadequate buildup can leave too little air during operation. A departure check should identify and resolve the problem rather than relying on the compressor to catch up on the road.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.3, physical PDF page 98, printed page 5-7. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
In the manual's low-speed service-brake check, a truck with normal air pressure pulls sharply to one side when braking from about 5 mph. What does that suggest?
Correct answer: The brakes may not be functioning correctly.
The low-speed check assesses stopping action and directional pull. Pulling to a side is a fault indication, not a satisfactory result.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.3.3, Test Service Brakes, physical PDF page 98, printed page 5-7. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
A truck has the familiar yellow, diamond-shaped push-pull parking-brake knob. Which action applies the parking brakes?
Correct answer: Pull the knob out.
On this control design, pulling applies the parking brakes and pushing releases them. Identify the actual controls on the vehicle; older systems may use other arrangements.
Source: Louisiana OMV-linked Commercial Driver License Manual, July 2017 cover version; section 5.1.15, physical PDF page 94, printed page 5-3. Equipment knowledge, not a claim about current Louisiana test scoring; actual vehicle instructions and supervised training remain necessary. ↗
