When marking a disabled commercial motor vehicle on a highway, where should you place flares or reflectors?

Placing flares or reflectors is crucial for ensuring safety and visibility when marking a disabled commercial motor vehicle on a highway. The correct distance of 30 metres (100 feet) to the front and rear of the vehicle provides a sufficient warning to approaching traffic. This distance strikes a balance between being far enough away to alert drivers from a significant distance, allowing time to react, while also not being so far that the markers could become less noticeable, especially in adverse weather conditions or poor visibility.

In practice, marking at this distance allows other drivers adequate time to observe the hazard and navigate safely around it, minimizing the risk of further accidents. The other options suggest distances that are either less effective or could potentially create confusion regarding the actual location of the disabled vehicle. Thus, 30 metres (100 feet) provides the optimal warning zone in line with highway safety regulations.