Final answer:
An air brake 'Q' endorsement is required when operating a truck with air brakes.
Step-by-step explanation:
An air brake 'Q' endorsement is required when operating a truck with air brakes. This endorsement is necessary because air brake systems operate differently than traditional brake systems, requiring additional knowledge and skills to operate safely.
When operating a truck with air brakes, drivers must be able to understand and control the air brake system, including the use of valves, gauges, and controls. They must also know how to conduct proper pre-trip inspections, recognize and address common air brake problems, and understand the importance of proper air brake maintenance.
By obtaining an air brake 'Q' endorsement, drivers demonstrate their understanding and competence in operating vehicles equipped with air brake systems.