What accessory must be functional for a vehicle to pass inspection?

For a vehicle to pass inspection, it's crucial that windshield wipers are functional. Windshield wipers play an essential role in maintaining visibility for the driver, especially in adverse weather conditions such as rain, snow, or fog. If the wipers do not work properly, it can lead to dangerous driving conditions, increasing the risk of accidents.

In the context of inspection criteria, while accessories like radios and air conditioning contribute to comfort and convenience, they do not impact the safety or operability of the vehicle in the same critical way as windshield wipers. Headlights are also vital for vehicle visibility and safety, but the primary focus for this question is on the specific requirement for passing inspection. Windshield wipers are deemed necessary to ensure that the driver has a clear view of the road during wet conditions, thus making their functionality a key aspect of the inspection process.