When should you downshift while driving?

Downshifting is an essential technique that helps maintain control of the vehicle in various driving situations. One of the key moments to downshift is before starting down a hill and before entering a curve. This action allows the driver to utilize engine braking, which helps slow the vehicle without over-relying on the brake system, thereby reducing the risk of brake overheating and maintaining better control.

When approaching a steep decline, downshifting to a lower gear enables the engine to assist in managing the vehicle's speed. This provides additional stability, especially on slippery or steep roads. In curves, downshifting not only prepares the vehicle for the upcoming maneuver but also ensures that power is available if needed for acceleration out of the turn.

This technique contrasts with other scenarios mentioned in the options. For example, downshifting when approaching a stop sign might not be necessary since there's typically an expectation to come to a complete stop, and downshifting on the highway at high speeds can disrupt stability if not done cautiously. Lastly, downshifting only when going uphill would not utilize the beneficial aspects of downshifting effectively, especially when managing speed in descending scenarios or tactile turns.