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 covered commercial truck is disabled on a rural highway shoulder where warning devices are required. When should the driver place them?
Correct answer: As soon as possible, and no later than 10 minutes.
Ten minutes is an outside deadline, not a suggested delay. Where the requirement applies, place the devices as soon as possible. Necessary traffic stops and the rule's special exceptions are different situations.
Source: 49 CFR 392.22(b)(1); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. Also Colorado CDL Manual (06/15/23), page 26. ↗
On a straight rural divided highway, an interstate truck is disabled on the shoulder with clear sight lines. Which triangle arrangement matches the federal rule?
Correct answer: One within 10 feet at the traffic side of the rear; others 100 and 200 feet toward approaching traffic.
For a divided or one-way highway, the two farther devices go 100 and 200 feet toward approaching traffic, centered in the occupied lane or shoulder. The nearest goes at the traffic side within 10 feet of the rear. An obstruction to sight can require adjusted placement.
Source: 49 CFR 392.22(b)(2)(v); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. Also Colorado CDL Manual (06/15/23), page 27. ↗
A covered truck is disabled on the shoulder of a straight, rural two-way road with no sight obstruction. Where do the two farther triangles go under the general federal arrangement?
Correct answer: About 100 feet ahead and 100 feet behind, in the occupied shoulder.
The general arrangement warns traffic from both directions: one device about 100 feet each way in the lane or shoulder occupied by the truck, plus a near device about 10 feet away on its traffic side toward approaching traffic.
Source: 49 CFR 392.22(b)(1)(i)-(iii); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. Also Colorado CDL Manual (06/15/23), page 27. ↗
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. ↗
An interstate truck is stopped with fuel leaking near the shoulder. What warning-device choice avoids adding an ignition source near the leak?
Correct answer: Use reflective triangles rather than lighting a flare near the fuel.
Do not introduce a flame where it could ignite leaking flammable liquid or gas. The federal rule prohibits a flame-producing warning at a distance that would not prevent a fire or explosion; reflective triangles avoid that ignition source.
Source: 49 CFR 392.22(b)(2)(vi); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. Also Colorado CDL Manual (06/15/23), page 27. ↗
An exit ramp curves sharply just after beginning downhill. Why should a truck driver assess it before entering?
Correct answer: The downhill section can build speed before the sharp curve.
A downgrade can increase speed on the approach to a ramp curve. Plan a suitable entry speed early; waiting until the curve leaves less room to control a heavy vehicle safely.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.8 Seeing Hazards; physical PDF page 33 (printed 33); reviewed September 14, 2026. ↗
Under the federal CMV texting rule, may a driver type a routine dispatch reply while stopped at a red light with the engine running?
Correct answer: No. A temporary traffic stop still counts as driving.
49 CFR 392.80 includes temporary traffic stops in its driving definition when the motor is running. A routine work message is not the emergency-communication exception.
Source: 49 CFR 392.80(a), (c) and (d); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. ↗
Which stop is outside the driving definition in the federal CMV texting rule?
Correct answer: Moving off the highway and halting where it is safe to remain.
The rule distinguishes a temporary traffic delay from moving to the side of or off the highway and halting where the vehicle can safely remain. Choose a genuinely safe location rather than stopping in a travel lane to text.
Source: 49 CFR 392.80(c); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. ↗
A carrier tells a driver to answer routine texts while driving a CMV. How does the federal texting rule apply to the carrier?
Correct answer: The carrier must not allow or require texting while driving.
49 CFR 392.80 prohibits a motor carrier from allowing or requiring a driver to text while driving. Dispatch needs must be handled without directing the driver to violate that rule.
Source: 49 CFR 392.80(b); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. ↗
Which communication fits the federal exception to the handheld-phone restriction while driving a CMV?
Correct answer: Necessary communication with emergency services about an emergency.
The exception is for communication necessary with law enforcement or emergency services. Routine business and personal calls do not qualify; this does not make a distracting or unsafe call a good driving choice.
Source: 49 CFR 392.82(a)-(c); eCFR title 49 displayed current through September 10, 2026; reviewed September 14, 2026. ↗
No train horn is audible as you approach a crossing. What can you safely conclude?
Correct answer: Nothing about whether a train is approaching; look and listen.
Train horns may not sound at some crossings, and cab noise can mask them. Silence is not permission to cross. Check the tracks and obey the warning devices and applicable stop rules.
Source: Colorado Commercial Driver License Manual (06/15/23), Section 2; 2.15.3 Driving Procedures; physical PDF page 43 (printed 43); reviewed September 14, 2026. ↗
