Final answer:
A tractor should not back under a trailer until the air system is at normal pressure to avoid brake failure or incomplete coupling, ensuring safe operation. option b is correct
Step-by-step explanation:
option b is correct You should not back a tractor under a trailer until the whole air system is at normal pressure. Operating a tractor-trailer combination safely requires that the air brake system is properly pressurized to ensure effective braking action and vehicle control. Backing under a trailer with insufficient air pressure can lead to brake failure or incomplete trailer coupling, creating the potential for an accident. It is crucial that the air system pressure is at the manufacturer's recommended level, which is typically around 120 to 140 psi for most commercial vehicles.
So, correct trailer coupling procedures necessitate ensuring the air system is fully pressurized to the normal operating range before attempting to back the tractor under the trailer.
When backing a tractor under a trailer, it is important to wait until the whole air system is at normal pressure. This ensures that the air brakes are functioning properly and will provide the necessary stopping power when needed.
For example, if the air system is empty or below normal pressure, the brakes may not engage properly, which can result in accidents or damage to the trailer. Therefore, it is crucial to wait until the air system reaches normal pressure before backing the tractor under the trailer.