An interstate truck's front tire has 3/32 inch of tread in a major groove. Does it meet the federal minimum for that position?
Correct answer: No. A front tire needs at least 4/32 inch.
For a truck, truck tractor or bus subject to this rule, front-wheel tires need at least 4/32 inch in a major tread groove, measured away from tie bars, humps and fillets. A 3/32-inch reading is below that minimum.
Source: 49 CFR 393.75(b); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. Also Colorado CDL Manual (06/15/23), page 16. ↗
During a walk-around, you notice new rust streaks extending from wheel nuts. What do they suggest?
Correct answer: The nuts may be loose and their tightness needs checking.
Rust trails can indicate movement at a wheel nut. Check the assembly rather than dismissing the streaks as cosmetic. The handbook also calls for a tightness recheck after a wheel has recently been changed.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.1.3 Wheel and Rim Problems; physical PDF page 17 (printed 17); reviewed September 14, 2026. ↗
A driver notices an exhaust leak beneath the sleeper area. Why must it be addressed?
Correct answer: Poisonous exhaust can enter the cab or sleeper.
A damaged exhaust system can let poisonous fumes into occupied spaces. Check leaking or unsecured exhaust components and have the defect corrected; opening a window is not a repair.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.1.3 Exhaust System Defects; physical PDF page 18 (printed 18); reviewed September 14, 2026. ↗
During the handbook's stationary hydraulic-brake check, the pedal keeps moving down while firm pressure is held. What does that indicate?
Correct answer: A possible leak or other fault that needs repair before driving.
A pedal that does not hold its position during this check can indicate a hydraulic leak or another brake problem. Get it corrected before driving. Air-brake vehicles require their own different checks.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.1.5 Test for Hydraulic Leaks; physical PDF page 22 (printed 22); reviewed September 14, 2026. ↗
A truck's drive wheels begin spinning as the driver accelerates on a wet surface. What is the appropriate immediate adjustment?
Correct answer: Ease off the accelerator to reduce the spinning.
Too much driving power for the available traction can make the wheels spin and threaten control. Reduce acceleration and build speed gradually when grip is poor.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.2.1 Accelerating; physical PDF page 23 (printed 23); reviewed September 14, 2026. ↗
Two suitable parking spaces are available. Which arrangement reduces a large vehicle's reversing risk?
Correct answer: The one that allows a forward departure when leaving.
Avoid reversing when a safe forward departure is practical. Backing exposes areas the driver cannot fully see, so parking position can remove an unnecessary maneuver.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.2.4 Backing Safely; physical PDF page 23 (printed 23); reviewed September 14, 2026. ↗
Before a helper guides a truck's reversing maneuver, what should both people agree on?
Correct answer: Clear hand signals, especially the signal to stop.
The driver and helper need a shared set of understandable signals, with a definite stop signal. Position the helper where the driver can see them and do not keep moving if communication or clearance becomes uncertain.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.2.4 Use a Helper; physical PDF page 23 (printed 23); reviewed September 14, 2026. ↗
Before a planned curve in a manually shifted truck, what preparation best supports control?
Correct answer: Reduce speed and select the appropriate gear before entering.
Complete the planned speed reduction and gear selection before the curve. This leaves the driver better able to steer smoothly without an avoidable shift or abrupt braking demand during the turn.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.3.1 Before Entering a Curve; physical PDF page 24 (printed 24); reviewed September 14, 2026. ↗
A car appears small and distant in a truck's convex mirror. What must the driver allow for?
Correct answer: It may be closer than its image makes it appear.
A convex mirror gives a wider view but makes objects look smaller and farther away. Account for that distortion when judging nearby traffic rather than treating apparent distance as actual clearance.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.4.2 How to Use Mirrors; physical PDF page 25 (printed 25); reviewed September 14, 2026. ↗
A driver sees an open-load tarp suddenly ballooning in the mirrors. What is the best response?
Correct answer: Treat it as a possible securement problem and check safely.
Mirrors can reveal developing cargo problems such as flapping covers or loose restraints. Investigate safely instead of waiting for a load to escape.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.4.2 Check Your Vehicle; physical PDF page 25 (printed 25); reviewed September 14, 2026. ↗
An interstate commercial truck breaks down on a highway shoulder. This is not a necessary traffic stop. Under the federal rule, what must the driver activate immediately?
Correct answer: The vehicle's hazard warning flashers.
The rule calls for immediate hazard flashers for this stop. Flashers must be used while required warning devices are being placed and picked up; they do not replace those devices.
Source: 49 CFR 392.22(a); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. Also Colorado CDL Manual (06/15/23), page 26. ↗
A disabled commercial truck is within 500 feet of a curve that hides it from approaching traffic. How does the federal rule address the warning in that direction?
Correct answer: Place it 100 to 500 feet from the truck where it gives ample advance warning.
When a curve, hillcrest or other obstruction limits the view in this situation, move the warning in that direction to a suitable point 100 to 500 feet from the truck. The purpose is to warn approaching road users early, not hide the device with the vehicle.
Source: 49 CFR 392.22(b)(2)(iv); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. Also Colorado CDL Manual (06/15/23), page 27. ↗
After unloading a truck, may the driver assume it can now follow closer because it must stop sooner?
Correct answer: No. Reduced tire traction can make an empty truck take longer to stop.
Do not assume less load guarantees a shorter stop. The handbook warns that reduced traction can make an empty truck's stopping performance worse. Leave a gap suitable for the actual vehicle and conditions.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.6.1 The Effect of Vehicle Weight on Stopping Distance; physical PDF page 28 (printed 28); reviewed September 14, 2026. ↗
A loaded truck has a high center of gravity. Does the speed posted for a curve guarantee that it will not roll over at that speed?
Correct answer: No. Its safe cornering speed may need to be lower.
A truck can roll over even while its tires retain grip. Load and center of gravity affect stability, so slow sufficiently before the curve rather than assuming the sign guarantees safety for the vehicle.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.6.3 Speed and Curves; physical PDF page 29 (printed 29); reviewed September 14, 2026. ↗
How can a driver measure the following gap without estimating a distance in feet?
Correct answer: Count the time from the lead vehicle passing a fixed landmark until the truck reaches it.
Choose a fixed point ahead and time the interval between the lead vehicle and your vehicle reaching that same point. Compare it with a suitable following-time guideline and drop back if needed.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.7.1 Space Ahead; physical PDF page 30 (printed 30); reviewed September 14, 2026. ↗
A low-clearance trailer approaches a sharply raised rail crossing. What should the driver establish before attempting to cross?
Correct answer: That the vehicle can clear the crest without getting hung up.
A long, low trailer can become stranded on a raised crossing even when its front wheels pass. Ground clearance and the road profile must be suitable; do not gamble on momentum to get over the crest.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.7.5 Space Below; physical PDF page 31 (printed 31); reviewed September 14, 2026. ↗
