What key factor affects emissions inspection results?

The vehicle's age and mileage are critical factors affecting emissions inspection results because they directly relate to the vehicle's overall condition and efficiency. As vehicles age, their engines may become less efficient and more prone to producing higher emissions due to wear and tear, outdated technology, and potential build-ups within the exhaust system. Additionally, the mileage can indicate how much the vehicle has been used and can correlate with the wear on engine components, fuel systems, and emission control systems. Therefore, older vehicles or those with higher mileage may struggle to meet current emissions standards compared to newer models that are typically designed to be more environmentally friendly. This relationship highlights the importance of considering both age and mileage when evaluating how a vehicle will perform in emissions testing.