Which item indicates a temporary speed restriction on a track?

A yellow flag is used to indicate a temporary speed restriction on a track in railroad operations. This flag serves as a warning to train crews that they must reduce their speed for a designated area ahead. The yellow color is a universally recognized signal for caution, alerting operators to be prepared to adjust their speed to ensure safety in potentially hazardous conditions or areas where track maintenance or other activities might be taking place.

In contrast, other flags serve different purposes in the railroad environment. For example, a green flag typically signals that it is safe to proceed, while a red flag indicates a stop signal or that there may be danger ahead. A white flag may signify a special indication less commonly related to speed restrictions. Understanding the specific meanings of these flags is crucial for safe train operations and compliance with regulations.