Final answer:
The parking or emergency brake on trucks and buses can only be held by a mechanism called a parking brake, which is a mechanical device that prevents the vehicle from rolling when parked or in an emergency. It is separate from the regular hydraulic brake system and is commonly engaged by pulling a lever or pushing a pedal.
Step-by-step explanation:
The parking or emergency brake on trucks and buses can only be held by a mechanism called a parking brake. This brake is typically a mechanical device that engages when the vehicle is parked, preventing it from rolling.
The parking brake is often located on the floor or operated by a hand lever near the driver's seat. It is separate from the regular hydraulic brake system and is designed to hold the vehicle in place when parked or in an emergency situation.
The parking brake is commonly engaged by pulling a lever or pushing a pedal, which activates a system that locks the rear wheels in place. This is important for larger vehicles like trucks and buses, as they may be parked on steep inclines or need to remain stationary during loading and unloading.