What is likely to happen if the service line comes apart while driving a combination vehicle?

When the service line comes apart while driving a combination vehicle, the situation typically leads to nothing happening immediately until the brakes are applied. This is because the service line is responsible for transmitting air from the truck's air system to the trailer, which controls the service brakes. If the line disconnects, the pneumatic pressure that keeps the service brakes released is lost; however, the brakes don't engage on their own until the driver applies them.

At this point, the driver may experience a delay in braking response since the emergency brakes, which rely on a different system, are designed to engage only under certain conditions, such as a complete loss of air pressure in the system. Therefore, the immediate impact of a disconnected service line might not be felt unless the driver attempts to stop, as normal braking functions rely on that continuous air pressure.

This understanding highlights the mechanics of how braking systems operate in combination vehicles, emphasizing the importance of maintaining the integrity of air lines during vehicle operation. The scenario underscores the necessity for drivers to be vigilant about the condition of their equipment and attentive to any changes in the vehicle’s handling.