Before starting a tractor-trailer engine, which action should you perform first?

Before starting a tractor-trailer engine, which action should you perform first?

• A. Turn the ignition switch on
• B. Apply the parking brake
• C. Depress the clutch
• D. Release the parking brake

Answer: (B)

Securing the vehicle before starting is the priority. Applying the parking brake locks the wheels, preventing any movement if the engine torque or a gear selection could otherwise cause the tractor-trailer to roll. This safety step is done first, especially on inclines or if the transmission might be in gear. After the parking brake is set, you would typically ensure the truck is in neutral (and depress the clutch if needed) before starting the engine. Releasing the parking brake or starting without this safeguard could allow an unintended roll, making the other actions unnecessary as the first step.

Securing the vehicle before starting is the priority. Applying the parking brake locks the wheels, preventing any movement if the engine torque or a gear selection could otherwise cause the tractor-trailer to roll. This safety step is done first, especially on inclines or if the transmission might be in gear. After the parking brake is set, you would typically ensure the truck is in neutral (and depress the clutch if needed) before starting the engine. Releasing the parking brake or starting without this safeguard could allow an unintended roll, making the other actions unnecessary as the first step.