What is the recommended action when leaving the driver's seat?

When leaving the driver's seat, it is crucial to take the key with you. This action helps to prevent unauthorized access to the vehicle, ensuring that no one can drive the bus in your absence. Securing the keys not only protects the vehicle itself but also enhances the safety of the passengers, as it curtails potential risks associated with an unattended bus.

While turning off the engine is a necessary practice when concluding a drive, it does not address the potential security issues that may arise if the keys are left in the ignition. Locking the door is also a good safety measure, but it only serves as a secondary line of defense if the keys are not secured. Notifying a supervisor is important for communication and operational purposes, yet it does not directly protect the vehicle from unauthorized use. Thus, taking the key is the most critical action to ensure overall safety and security when leaving the driver’s seat.