If a freight train is going under medium speed, how fast can it travel?

In the context of freight trains and their speed classifications, "medium speed" typically refers to a range of speeds that allows for safe operation while balancing factors such as train weight and track conditions.

The correct answer indicates that under conditions considered to be medium speed, freight trains can often travel at a pace where 30 mph is a common standard. This speed is generally seen as a safe operational limit, accommodating various considerations including stopping distances and the weight of freight loads.

The speeds above 30 mph, such as 40 mph or 50 mph, could fall into a different category, potentially classified as "high speed" depending on the regulations and safety standards in place. However, 35 mph fits within the spectrum of what can also be seen under medium speed, but a specific limit like 30 mph is often defined for safety. Thus, selecting 30 mph reflects a conservative and standard understanding of medium speed for freight trains.