What should the speed be for trains moving when a block system is not in effect?

The appropriate speed for trains operating when a block system is not in effect is determined by the principle of safety and visibility. When there is no block system, which typically provides protections against collisions and ensures safe distances between trains, the responsibility falls heavily on the engineer or train operator to maintain control over the train's speed.

Choosing a speed that allows the train to stop within half the range of vision is critical for safety. This practice ensures that if an unexpected obstacle or hazard suddenly appears on the track — such as a stalled train, a washout, or a fallen object — the engineer will have sufficient time to react and bring the train to a stop before reaching that hazard.

This method of speed management emphasizes situational awareness and allows for quick decision-making based on the visual conditions ahead, which is especially important in environments where visual cues dictate operational safety.

Other options might suggest reckless practices or insufficient controls for safe operation, such as operating at maximum speed without regard for potential hazards, or using subjective comfort levels that do not provide a clear guideline for safety. Thus, adhering to the speed limit correlated to stopping within half the range of vision is a fundamental safety protocol in rail operations when no block system is in effect.