After requesting permission to pass a stopped automatic signal, what must the engineer do?

After requesting permission to pass a stopped automatic signal, the engineer must switch to 'Release' and stop the head car. This procedure ensures the safety of the operation by allowing the engineer to maintain control over the train while ensuring that it is in a safe state before proceeding. The 'Release' function indicates that the engineer has received permission and is ready to move the train past a signal that may have previously indicated to stop.

Stopping the head car is a critical step as it allows the engineer to verify that the track ahead is clear and safe for movement. It also provides an opportunity to address any potential issues or receive further instructions if necessary before proceeding, thus emphasizing the importance of caution in handling signals.

The other choices do not align with established protocols. For example, proceeding without stopping could lead to dangers if the path ahead is not properly assessed. Similarly, waiting for further instructions may not be necessary if permission has already been granted to move. Reducing speed immediately without stopping does not provide a clear indication of readiness to continue at a safe and controlled pace.