What are acceptable pressure levels for the air supply valve and park control valve in a pre-trip air brake inspection?

During a pre-trip air brake inspection, it is essential to ensure that the air supply valve and the park control valve are functioning correctly by verifying their pressure levels. The correct pressure levels are critical for the proper operation of the braking system. In this context, the acceptable levels for the air supply valve are typically set at around 50 PSI, which ensures that there is enough air pressure to engage the braking system effectively. The park control valve, which is used to apply the parking brake, should typically be set at an acceptable level of 30 PSI, ensuring that the brakes can hold the vehicle stationary when parked.

Having these specific pressures ensures that drivers can trust the functionality of their braking systems, which is crucial for safe operation on the road. Pressure levels that are too low may result in inadequate braking performance or failure of the parking brake, which could lead to unsafe driving conditions. The choice provided accurately reflects these requirements for maintaining safe operating standards in commercial vehicles.