Under what circumstances might a vehicle's lights fail inspection?

A vehicle's lights may fail inspection primarily if any bulbs are burned out or not functioning properly. This is a crucial safety consideration, as properly functioning lights are essential for visibility and signaling on the road. During the inspection, mechanics check to ensure that all lights, including headlights, taillights, turn signals, and brake lights, are operational. If any one of these bulbs is not working, it can compromise the safety of the vehicle, making this condition a valid reason for failing the inspection.

Issues such as brightness or matching the original equipment specifications are less direct indicators of safety. While excessively bright lights may cause glare and be a concern for other drivers, it is typically the functionality of the lights that is prioritized during inspections. Flickering lights may suggest an electrical issue, but the immediate concern in a safety inspection focuses on whether the lights work consistently and effectively, which gets back to the fundamental requirement of bulbs needing to be operational. Hence, a non-functioning bulb represents a more clear-cut criterion that directly impacts safety on the road, leading to the understanding that failing to function properly is the main reason for failing inspection.