What is NOT part of the brake system during an inspection?

Answer: A — Auxiliary lights

The brake system of a commercial vehicle is crucial for safety and includes various components specifically designed to ensure effective braking. During an inspection, it is important to evaluate parts that directly impact the brake functionality. Auxiliary lights, while they contribute to the overall visibility and safety of the vehicle, do not play a role in the braking system itself. The brake system consists of essential components such as check valves, compressors, and relay emergency valves, which all function to create, maintain, and manage braking pressure. Check valves help prevent air from escaping from the system, compressors generate air to operate the braking mechanism, and relay emergency valves ensure that the air supply remains pressurized to apply the brakes in emergency situations. Understanding this distinction highlights why auxiliary lights do not belong to the brake system during an inspection.