How do heavy-duty vehicles differ in emissions testing compared to light-duty ones?

Heavy-duty vehicles are indeed subject to different standards and testing procedures compared to light-duty vehicles primarily due to their size and usage. These vehicles typically include trucks and buses that are designed for heavier loads and often operate under more demanding conditions. As a result, the emissions they produce can differ significantly from those of light-duty vehicles.

The emissions testing for heavy-duty vehicles takes into account factors such as engine size, weight, and the types of fuel used. These vehicles often have more stringent regulations because they contribute a larger share of certain pollutants, particularly nitrogen oxides (NOx) and particulate matter (PM). Testing procedures are tailored to better reflect real-world operating conditions for heavy-duty vehicles, which can include different drive cycles and test methodologies.

In contrast, the other choices incorrectly describe the relationship between heavy-duty and light-duty vehicle emissions testing. Testing procedures are not the same for both categories, and heavy-duty vehicles are not exempt from testing; they are crucial for ensuring compliance with environmental regulations. The notion that heavy-duty vehicles are only tested for noise pollution overlooks the broader scope of emissions regulations that addresses various harmful emissions from these vehicles.