When should a Class II brake test be performed?

A Class II brake test is a critical procedure that must be conducted to ensure the safety and proper functioning of the vehicle's braking system. It is particularly essential to perform this test before departure to verify that the brakes are in optimal condition and can effectively stop the vehicle as needed. This proactive measure helps to prevent accidents and maintain compliance with safety regulations.

The requirement for the test to be conducted at all times prior to leaving the terminal or under certain conditions emphasizes the importance of readiness in various operational scenarios. For instance, conditions like changes in environmental factors or after a vehicle has been out of service may necessitate an additional brake test, further underscoring the need for thorough checks before the vehicle is put into operation.

The other options suggest more limited circumstances under which the test may be conducted, which does not align with the safety protocols that prioritize preventive measures and regular checks to ensure the vehicle's reliability and safety. Thus, the comprehensive approach to performing the brake test outlined in the correct answer is crucial for maintaining a safe operating environment.