What speed indicates that all work must stop on an adjacent controlled track for freight trains?

The correct answer is based on the rules and regulations that govern train operations and safety in the vicinity of work areas on tracks. Specifically, when freight trains are operating at a certain speed, it triggers a requirement for all work to cease on adjacent controlled tracks to ensure safety.

In this case, a speed of 25 mph signifies that the risk of a passing train could pose a danger to any ongoing work or personnel in the area. The reason this speed is critical is due to the potential impact and the effects of a train moving at that velocity, which complicates issues like reaction time, safety protocols, and communication among workers and train operators.

Understanding this threshold is essential for maintaining safety and preventing accidents during railway operations. It emphasizes the need for stringent adherence to speed regulations in work zones where personnel and equipment are present.