During an inspection, when must the headlights be turned on?

The headlights should be turned on during the inspection to test the operation of signaling devices and stoplights. This step is essential because it ensures that the lights function properly in conjunction with the vehicle’s signaling system. By having the headlights illuminated, the inspector can better assess if the vehicle's turn signals, brake lights, and other lighting mechanisms are operating correctly. This is crucial for safety and ensuring compliance with the regulations that govern vehicle operation.

In contrast, activities like inspecting tire pressure, testing the horn, or checking windshield wipers do not necessitate the headlights being on, as those functions are unrelated to the vehicle's lighting systems. Hence, the requirement to check headlights is specifically tied to ensuring proper signaling and stopping visibility.