Car safety inspections vary based on the state, but inspectors often look at the car for signs of rust or anything else that could compromise the car's structural integrity. Tires are usually included on the checklist as well to make sure they are not at risk of bursting.
Safety inspections also often place an emphasis on the car's ability to brake quickly enough; worn tires can fail the car since they increase the emergency braking distance. The brakes themselves are generally on the inspection list, and worn brake pads and mechanical issues can lead to a failure.
Visibility is a critical component of car safety, so inspections generally look at the windshield and other windows. A crack on the windshield can lead to a failure, and significant smudges or other obstructions may need to be fixed before the car can pass inspection. Window tint is often regulated, so some inspections require the inspector to note illegal tinting.
Car horns are required in most states, so inspections often check to make sure the horn works correctly. The car's lighting is important as well, and drivers can expect the inspector to check the operation of brake and running lights in addition to the headlights.