Ontario MTO Truck Knowledge Practice Test

Selecting the appropriate gear before descending a grade is crucial for maintaining control of the vehicle and ensuring safety. When a truck is driven downhill, gravity can increase the speed of the vehicle. Therefore, choosing a lower gear allows the engine to help slow the truck through engine braking, which reduces reliance on the brakes alone. This practice helps prevent brake overheating and potential failure, leading to a safer descent.

The other options would not be advisable actions before descending. Turning off the engine could lead to a loss of control, as steering and braking would be compromised. Speeding up contradicts the need for control when going downhill, increasing the risk of losing control. Quickly applying the brakes can result in brake failure due to overheating, and it is not the most effective method to manage speed on a grade.