Which of the following is NOT a proper use of vehicle lights?

Flashing brake lights to deter a tailgating driver is not a proper use of vehicle lights. Brake lights are intended to signal that the driver is slowing down or stopping, which is crucial for maintaining safety on the road. Using them to communicate with other drivers in a way that is not their intended purpose, such as to dissuade tailgating, could lead to confusion and potentially dangerous situations.

In contrast, the other options represent correct and safe practices for using vehicle lights: headlights increase visibility during poor conditions, turn signals effectively communicate lane changes to other drivers, and emergency flashers serve to alert other road users when a vehicle is stopped in a hazardous location. Each of these uses aligns with safe driving practices and contributes to overall road safety.