Taking into account the order to secure vehicles during stops, should all the doors remain closed when the tram driver is in the cabin?

The requirement to secure a vehicle is intended to prevent its use by an unauthorised person, especially when it is left unattended. In a situation where the tram driver is in the cab, they maintain constant control over the tram, which constitutes a sufficient safeguard. For this reason, there is no requirement to close all the doors.