Which of the following are acceptable warning devices for a disabled truck, bus, or tractor-trailer on a traveled roadway?

The correct answer highlights the use of emergency reflective triangles and liquid-burning flares as acceptable warning devices for a disabled truck, bus, or tractor-trailer on a traveled roadway. These devices are specifically designed to alert approaching drivers to the presence of a stationary vehicle, enhancing safety for both the operator of the disabled vehicle and other road users.

Emergency reflective triangles are a crucial safety feature because they are highly visible and can be set up at varying distances from the disabled vehicle to warn oncoming traffic effectively. They are particularly valuable because they do not rely on lighting conditions; they can be seen both day and night.

Liquid-burning flares serve a similar purpose, providing a visual alert through fire that can attract attention from greater distances. They are particularly useful in low-light conditions, where visibility might be compromised.

For other options, the reference to emergency kit items only being used in daylight does not provide the immediate, visible warnings required for nighttime or low-visibility situations. Similarly, while horn alerts can be useful for drawing attention when a vehicle is moving, they are not effective as stationary warning devices. Lastly, reflective vests and cones may not provide the same level of visibility or distance coverage compared to the approved warning devices specified in the correct answer. This distinction is