What leads to the automatic failure of a vehicle inspection?

A vehicle inspection can result in an automatic failure if there is any fluid leak, which includes brake fluid. The presence of a fluid leak is a critical safety concern for a vehicle. Brake fluid, in particular, is vital for the proper functioning of the braking system. If there is a leak, it could indicate that there is a serious issue that could compromise the vehicle's ability to stop effectively, posing a significant risk to the driver, passengers, and others on the road. Inspectors are trained to regard any fluid leaks as failures because they represent potential hazards that need to be addressed to ensure the vehicle is safe for operation.

The other options, while they can indicate maintenance issues or might lead to a failed inspection under certain circumstances, do not carry the same immediate risks associated with fluid leaks. For example, visible mud on tires is typically more of a cleanliness issue and does not directly relate to vehicle safety. Low tire pressure affects handling and can lead to tire blowouts, but it may be remedied before considering a failure. Non-functioning interior lights may affect visibility for occupants but do not impact the operational safety of the vehicle in the same way that a fluid leak does.