What is a critical requirement of a safety inspection for headlights?

A critical requirement of a safety inspection for headlights is that they must be properly aligned and functioning. This ensures that the headlights illuminate the road ahead effectively and do not cause glare for oncoming drivers. Proper alignment is essential because misaligned headlights can lead to reduced visibility during nighttime driving, increasing the risk of accidents. Functioning headlights contribute to safe driving conditions by making the vehicle visible to others and allowing the driver to see clearly.

The other options do not address the primary safety concerns related to headlights. For instance, ease of replacement and the type of bulb used, such as high-intensity discharge lights, do not inherently relate to the operational safety of the vehicle. Additionally, while headlights may need to be turned off during certain inspections for practical reasons, this requirement does not contribute to the ongoing safety and functionality of the lights in a real-world driving scenario.