What indicator is mandatory for vehicles with multiple beam headlights?

The correct answer focuses on the requirement for a beam indicator that illuminates specifically when the high beam is activated. This is important for ensuring that drivers are aware of their headlight settings, particularly in situations where using high beams is inappropriate or could blind oncoming drivers. A dedicated high beam indicator serves as a crucial safety feature, helping to prevent accidents by ensuring that drivers do not unintentionally use high beams when they should be using low beams.

In many states, including Missouri, compliance with these regulations is key for vehicle safety inspections. The presence of this indicator not only assists the driver in maintaining proper illumination but also helps in communicating the vehicle’s headlight status to other road users.

The other choices might focus on various indicators related to headlight usage, but the specific requirement for a beam indicator that lights up when high beams are in use is the standard protocol to enhance road safety.