If there is a failure in the trailer supply line, what will happen to the spring park brakes?

When there is a failure in the trailer supply line, the spring park brakes will apply immediately. This occurs because the system relies on the presence of air pressure in the supply line to keep the spring brakes released. In the event of a failure, the air pressure drops, allowing the powerful springs in the brake assembly to engage the brakes automatically. This safety feature is designed to prevent the trailer from rolling or moving unintentionally, ensuring that it remains securely in place when the air supply is compromised.

The immediate application of the spring park brakes is a crucial safety mechanism that helps to mitigate the risk of accidents when there is a loss of air pressure, thus providing a reliable response in case of a system failure.