Seeing this signal, must the tram driver regardless of the circumstances stop the vehicle?

The visible signal of a horizontal bar, displayed by the S-2 signal, means the tram driver is prohibited from proceeding past the signal. However, instructions and signals given by persons directing traffic take precedence over traffic light signals. Therefore, if an authorised person (e.g., a police officer) were to instruct the driver to proceed, the tram driver would not be required to stop.