On a vehicle without ABS, what defines controlled braking during an emergency stop?
Correct answer: Brake as hard as possible without locking the wheels
For controlled braking, brake firmly without locking the wheels and keep steering movements small. If wheels lock or a larger steering correction is needed, release the brakes and reapply as soon as possible. This question concerns a vehicle without ABS.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.4.3 Emergency Stops — Controlled Braking, printed 5-9 (physical PDF page 103) ↗
Which extra factor is part of total stopping distance for an air-brake vehicle?
Correct answer: Brake lag distance
Air needs time to reach the brakes, adding brake lag to perception, reaction, and braking distances.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.4.4 Stopping Distance; total-distance formula, printed 5-9 (physical PDF page 103) ↗
At 55 mph on dry pavement, approximately how much distance can air-brake lag add?
Correct answer: 32 feet
The handbook estimates about 32 feet of brake-lag distance at 55 mph.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.4.4 Stopping Distance, printed 5-9 (physical PDF page 103) ↗
What is a primary cause of brake fade on a long downgrade?
Correct answer: Excessive service-brake use and heat
Overuse creates heat that reduces lining friction and expands drums, weakening braking.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.4.5 Brake Fading or Failure, printed 5-9 (physical PDF page 103) ↗
What should a driver do when the low-air warning activates on the road?
Correct answer: Stop and park safely as soon as possible
A warning may indicate a leak; stop safely before pressure falls far enough for spring brakes to apply.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.4.7 Low Air Pressure, printed 5-10 (physical PDF page 104) ↗
Before moving a vehicle with a dual air brake system, what should you confirm on both pressure gauges?
Correct answer: Both systems have reached at least 100 psi
The handbook instructs drivers to allow pressure to build to at least 100 psi in both systems before driving. Check both gauges rather than assuming one charged circuit means the other is ready.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.2 Dual Air Brake Systems, printed 5-6 (physical PDF page 100) ↗
One circuit of a dual air brake system loses pressure while you are driving. Why must you stop safely and obtain repairs?
Correct answer: The remaining circuit does not provide normal braking at all wheels
A failure in one circuit can leave part of the vehicle without working service brakes. Stopping distance increases, so bring the vehicle to a safe stop and have the system repaired before continuing.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.2 Dual Air Brake Systems, printed 5-6 (physical PDF page 100) ↗
What should you inspect on a belt-driven air compressor during the engine-compartment check?
Correct answer: Belt condition and tightness
A loose or damaged drive belt can prevent correct air supply. Section 5.3.1 calls for checking the belt condition and tightness.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.3.1 During Step 2 Engine Compartment Checks, printed 5-6 (physical PDF page 100) ↗
An automatic slack adjuster repeatedly has excessive stroke. What is the appropriate response?
Correct answer: Have the underlying brake problem diagnosed and repaired
Excessive stroke with an automatic adjuster can indicate a mechanical problem. Routine manual adjustment can conceal the defect and is not a substitute for qualified repair following the manufacturer’s procedures.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.3.2 During Step 5 Walkaround Inspection — automatic slack adjusters, printed 5-6 (physical PDF page 100) ↗
After its normal startup check, an ABS warning lamp comes on while the vehicle is moving. What does this suggest?
Correct answer: A possible ABS malfunction that needs attention
An ABS malfunction lamp that remains on after the appropriate check or comes on during travel can indicate an ABS fault. Normal braking remains, but the fault needs service; follow the vehicle-specific lamp-check procedure.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.1.16 Antilock Braking Systems, printed 5-4 (physical PDF page 98) ↗
Which benefit should you expect from ABS during hard braking?
Correct answer: Reduced wheel locking, helping you retain vehicle control
ABS helps prevent wheel lock during hard braking. It supports control but does not necessarily shorten stopping distance and does not replace careful speed or following-distance choices.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.1.16 Antilock Braking Systems, printed 5-4 (physical PDF page 98) ↗
Brakes are very wet and temperatures are freezing. What parking precaution does Pennsylvania's air-brake chapter describe?
Correct answer: Use wheel chocks on a level surface instead of applying wet parking brakes
Very wet parking brakes may freeze in place. Secure the vehicle with wheel chocks on level ground; never leave it able to roll.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.4.8 Parking Brakes, printed 5-10 (physical PDF page 104) ↗
During a brake inspection, you find oil or grease on a brake lining. How should this be treated?
Correct answer: As a brake defect that needs correction
Brake linings should not be loose or contaminated with oil or grease. Normal air pressure does not make a defective friction surface safe; the defect needs correction.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.3.2 During Step 5 Walkaround Inspection — Check Brake Drums (or Discs), Linings, and Hoses, printed 5-7 (physical PDF page 101) ↗
An older truck has a manual front brake limiting valve marked NORMAL and SLIPPERY. Which setting normally preserves full front braking?
Correct answer: NORMAL
The manual limiting valve reduces front brake pressure in the SLIPPERY position and can reduce stopping ability. The handbook says to leave this type of control in NORMAL for normal stopping power.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.1.13 Front Brake Limiting Valve, printed 5-3 (physical PDF page 97) ↗
What should you look for when inspecting the flexible air hoses connected to brake chambers?
Correct answer: Damage or wear caused by rubbing
Inspect brake hoses for damage and wear from rubbing. A damaged hose can lose air; a normal pressure reading does not make the defect acceptable.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.3.2 During Step 5 Walkaround Inspection — Check Brake Drums (or Discs), Linings, and Hoses, printed 5-7 (physical PDF page 101) ↗
Which three functions make up the air-brake system described in the handbook?
Correct answer: Service, parking, and emergency braking
The functions serve normal stops, parking, and brake-system failures.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), Section 5 introduction, printed 5-1 (physical PDF page 95) ↗
In normal service braking, pressing the pedal farther does what?
Correct answer: Sends greater application pressure to the brakes
Pedal force controls service-brake application pressure.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.1.7 The Brake Pedal, printed 5-2 (physical PDF page 96) ↗
An air compressor has its own oil supply rather than engine lubrication. What should you check before driving?
Correct answer: Its oil level
A separately lubricated compressor needs its own oil check.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.1.1 Air Compressor, printed 5-1 (physical PDF page 95) ↗
Does an alcohol evaporator eliminate the need to drain manually drained air tanks?
Correct answer: No, tank drainage is still required
The evaporator helps reduce freezing risk; it does not remove accumulated water and oil.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.1.5 Alcohol Evaporator, printed 5-2 (physical PDF page 96) ↗
The air-system safety valve releases air. What does this indicate?
Correct answer: A fault requiring mechanical attention
The safety valve is a pressure safeguard, not the ordinary compressor control.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), section 5.1.6 Safety Valve, printed 5-2 (physical PDF page 96) ↗
