What should be ensured for every motor vehicle equipped with brakes?

The requirement that every motor vehicle equipped with brakes must utilize one control device is fundamental for effective control and safety during operation. Each vehicle is designed with a specific brake control system that allows the driver to engage and release the brake system effectively. This single control device—typically a pedal in passenger vehicles or a lever in some commercial vehicles—ensures that the driver can easily and promptly activate the brakes when necessary.

This design is critical because it simplifies the operation of the vehicle's braking system, ensuring that drivers can react swiftly in emergency situations. Moreover, using a single control device allows for standardized training and familiarity, ensuring all drivers understand how to operate the vehicle safely and efficiently.

While having more than one brake control device might seem beneficial in terms of redundancy, it could complicate operation and create confusion. The other options, while they may intend to address safety and maintenance, do not focus on the essential requirement for brake control in terms of active operation and user interface.