What signal must you give to a policeman when you are about to go straight ahead?

To communicate your intention to drive straight ahead in the presence of a policeman, you should raise your hand towards the shoulder and move your forearm forward and back. This signal is clear and recognized by law enforcement as an indication that you are continuing straight, and it helps ensure that your intentions are understood. Proper signaling is essential for maintaining safety and clarity on the road, especially when interacting with traffic authorities who may be directing movement.

Other options do not convey the intended direction clearly in the context of driving straight ahead. Waving your hand out of the window can be ambiguous and might not provide enough clarity to the policeman about your intent. Extending your left arm is typically used to signal a left turn, which does not apply in this situation. Flashing your headlights is often used for alerting other drivers but is not specifically accepted as a signal for going straight ahead. Thus, raising your hand towards the shoulder and moving your forearm is the most effective and recognized method for indicating that you will proceed straight ahead.