Why do heavier vehicles generate more emissions?

Heavier vehicles generate more emissions primarily because they require more power and fuel to operate efficiently. As the weight of a vehicle increases, the engine must work harder to overcome the greater inertia both during acceleration and while maintaining speed. This results in higher fuel consumption since the engine burns more fuel to produce the necessary power. Furthermore, heavier vehicles often have larger engines that inherently produce more emissions due to their increased fuel consumption and the combustion process.

The other options, while they touch on various aspects of vehicle design and operation, do not directly relate to the primary reason for increased emissions. For example, larger tires may contribute marginally to fuel consumption and emissions, but they are not the main factor. Speed is not a significant contributor to emissions when discussing weight specifically, as emission generation is more closely linked to power requirements. Lastly, while carrying more passengers can increase weight, the key factor in emissions is tied to the power needed to operate the vehicle, making the emphasis on fuel and power usage central to understanding why heavier vehicles emit more pollutants.