What is the most effective method for handling a heavy load on a downhill grade?

Using lower gears to control speed is the most effective method for handling a heavy load on a downhill grade because it allows the engine to provide additional braking power through compression. When you shift to a lower gear, the engine helps slow the vehicle down, which reduces the reliance on the brake system alone. This is crucial for maintaining control, particularly with heavy loads, as brakes can overheat and become less effective if used continuously or excessively.

Lower gears increase the engine's RPM, which in turn helps to improve vehicle stability and reduces the chances of losing control. This technique, known as engine braking, is particularly important in mountainous areas or steep grades where the likelihood of brake failure due to overheating is a significant risk.

Other methods, such as accelerating to maintain momentum or using higher gears, can lead to unsafe situations, particularly with heavy loads, as they do not provide adequate control or braking power. Applying brakes continuously can also lead to brake fade, further compromising safety. Thus, using lower gears is the safest and most effective strategy for managing a heavy load on downhill grades.