What are the maximum allowable leakage rates for combination vehicles?

The maximum allowable leakage rate for combination vehicles is indeed less than 4 psi in one minute. This standard is important for ensuring the integrity of the air brake system in combination vehicles, which includes both tractor-trailers and larger truck configurations. Maintaining a leakage rate below this threshold is essential for proper brake function, which is critical for the safety of the vehicle and its ability to stop effectively.

If the leakage rate were higher than 4 psi per minute, it would indicate that there is a significant air leak present within the brake system. This can lead to reduced brake pressure, compromising the vehicle's braking capabilities and increasing the risk of accidents. Therefore, the specification helps to enforce vehicle maintenance standards that promote safe operation on the road.

The other listed rates are lower than the acceptable limit for leakage in combination vehicles, but they do not align with established safety regulations that govern vehicle maintenance practices.