What is considered normal speed for a train?

The concept of "normal speed" for a train often refers to the maximum speed that the train is allowed to travel under specific conditions as defined by governing authorities and regulations. This speed is determined after considering various factors such as the type of service the train is operating (commuter, freight, etc.), track conditions, and safety protocols in place.

Selecting the maximum speed allowed as the definition of normal speed is appropriate because it encompasses the operational limits within which a train is designed to function safely and efficiently. It takes into account the engineering standards for the equipment and allows for the necessary flexibility depending on route and operational requirements.

In contrast, the other options indicate specific speed limits that may apply under certain circumstances or for particular types of trains or service areas. These limits are often designed to ensure safety but do not define the broader concept of normal speed which aligns with operational maximums in regular service contexts.