How should the driver be signaled to start the engine at night?

The correct answer is moving a light in a horizontal figure 8 in a vertical plane to signal the driver to start the engine at night. This method effectively communicates the command due to its distinctiveness and clarity in low-light conditions. The motion creates a recognizable pattern that can be easily seen from a distance, ensuring that the driver understands it is time to start the engine.

In nighttime scenarios, visibility is low, and common signals, such as static lights or simple gestures, can be easily misinterpreted. The horizontal figure 8 provides both movement and shape that stands out, reducing the risk of miscommunication.

Other methods, such as flashing headlights rapidly or holding a flashlight above the head, may not be as pronounced or easily discernible, especially at a distance, potentially leading to confusion about the signal. Tapping the side of the vehicle also lacks the visibility and clarity required at night, as it does not incorporate the use of light to convey the message effectively.