Connecticut CDL Combination Vehicles Permit Practice Test

When both air lines are pulled apart due to a trailer breaking away while driving, it causes the trailer's brakes to activate. This happens because the air line that supplies compressed air to the trailer's braking system gets disconnected, which triggers the trailer's emergency brake system. The brakes are designed to engage automatically when there is a loss of air pressure in the system. This mechanism is a safety feature intended to prevent the trailer from rolling away uncontrollably.

The other options do not accurately describe the situation. The tractor does not stop immediately, as the separation of air lines primarily affects trailer brakes rather than the propulsion of the tractor. The emergency lights are not automatically activated by this incident, as their functionality is independent of the trailer brake system. Lastly, the engine revving higher is not related to the disconnection of air lines; instead, this could be a misinterpretation of the vehicle's response to a loss of load or braking system engagement. Understanding that the trailer's brake system is designed for safety is crucial for anyone operating combination vehicles.