What are the three levels of speed restrictions for heat conditions?

The correct answer reflects specific thresholds for speed restrictions that are implemented during heat conditions to ensure safety and reduce the risk of track-related issues. These speed levels are established based on the understanding that higher temperatures can lead to track expansion, which could result in track instability or failure.

In the context of heat conditions, setting speed restrictions at less than 100 mph, less than 80 mph, and less than 30 mph serves as a safety measure to prevent accidents and maintain control over trains operating on potentially compromised tracks. This tiered approach allows for varied responses based on the severity of heat-related impacts on the rail infrastructure, thus prioritizing the safety of both passengers and crew.

The other options do not align with the established benchmarks for heat-related speed restrictions. They either set thresholds too low or too high in comparison to what is recognized in practice, which could compromise safety during extreme weather conditions. Understanding these systemic protocols is essential for anyone involved in train operations and dispatching, as they directly influence operational decisions and risk management strategies.