Where must the required words be displayed on a patrol car with an amber light bar?

The correct choice is that the required words must be displayed on the rear and both sides of a patrol car equipped with an amber light bar. This regulation is in place to ensure that the vehicle is clearly identified as an emergency or service vehicle while providing maximum visibility from various angles. Displaying the identification on multiple sides helps in maintaining public awareness and safety, especially in situations where the vehicle may be responding to emergencies on busy roads or during low-light conditions.

Considering the other options, displaying the words only on the front would limit visibility and identification to drivers approaching head-on, neglecting individuals in other positions. Showing identification solely under the windshield would similarly restrict visibility and may not be easily legible to other drivers or pedestrians. Having the words only on the roof would make identification difficult for vehicles approaching from the side or rear, which is not practical for the vehicle's operation in traffic or emergency situations.