In which situation should signal lights be used while driving?

Answer: B — Before changing lanes or turning

Signal lights should be used before changing lanes or turning because they serve a crucial safety function on the road. By signaling your intentions, you communicate to other drivers and pedestrians what you plan to do, allowing them to adjust their actions accordingly. This helps to prevent accidents and ensures smooth traffic flow. Using signals before lane changes or turns is a legal requirement in most jurisdictions, including Nova Scotia. It reflects responsible driving behavior and consideration for other road users. Proper use of signal lights helps to convey your intentions clearly and maintains predictability in driving, which is essential for road safety. In contrast, other situations listed either do not appropriately utilize signals or could lead to confusion regarding a driver's intentions. For instance, signaling only when in doubt might cause unnecessary uncertainty for other drivers. Similarly, while it's important to signal when parking, it is not as critical as signaling before making active maneuvers like lane changes or turns. The option suggesting to signal only in heavy traffic undermines the consistent need for clarity in communication on the road, regardless of traffic conditions.