When may the speed of a train be increased after passing a temporary speed restriction area?

The correct response is that a train may increase its speed after passing the Temporary Resume speed sign. This sign indicates that the temporary speed restriction has ended, and the train can safely resume a higher speed. The presence of this sign is crucial because it provides specific and clear guidance to the engineer on when it is permissible to accelerate back to normal operational speeds.

The Temporary Resume speed sign serves as an official marker that signifies the end of the temporary restriction, ensuring that both the train crew and the signaling system are aligned on the new speed parameters. This structured approach helps maintain safety and operational consistency within the rail system.

While a signal change or other events might seem like valid indicators to resume speed, they do not provide the specific confirmation regarding the end of a temporary speed restriction. Thus, relying solely on a signal change or on other cues, like the conductor's signal, may lead to misunderstanding and potentially unsafe conditions if those cues are not aligned with the status of the speed restrictions.