What is the most important hand signal that should be agreed upon between a driver and a helper?

The signal for STOP is crucial as it ensures the safety of both the driver and the helper. It prevents accidents by providing a clear and immediate indication that any movement must cease. With the potential dangers associated with driving, particularly for larger vehicles and when working in collaboration with another person, having an unmistakable signal for stopping can prevent mishaps that could result from miscommunication. The STOP signal helps to establish a precautionary measure that allows for safer operations, especially in situations involving loading and unloading or navigating tight spaces.

While signals for go, turn, and slow down are also important, the STOP signal is ultimately the most critical for immediate safety. It serves as an essential safeguard that can avert collisions or other accidents, making it paramount in terms of prioritizing safety in any driving situation.