What is indicated by a marker on the rear of a train?

The marker on the rear of a train serves a vital safety function by indicating the train's presence to other trains and railroad employees. Specifically, it often consists of a reflector, flag, or light that is usually in the red-orange-amber color range. This coloring is universally recognized for signaling caution and alerting oncoming traffic about the presence of the train, especially in low visibility conditions or at night.

The other choices do not accurately represent the function of a rear marker. For instance, a train’s schedule and the available passenger services are not conveyed by this indication. Additionally, while maximum speed limits are important, they are not communicated through a rear marker but instead can be represented by signage along the tracks and in other regulatory contexts.