What is the primary benefit of carpooling in relation to environmental impact?

The primary benefit of carpooling in relation to environmental impact is that it leads to having fewer vehicles on the roadway. This reduction in the number of vehicles actively helps to decrease traffic congestion, lowers greenhouse gas emissions, and minimizes fuel consumption. By sharing rides, carpooling reduces the overall number of trips made, which directly contributes to less air pollution and a smaller carbon footprint. Additionally, fewer vehicles mean less wear on road infrastructure and potentially reduced costs associated with road maintenance and expansion.

In contrast, the other options focus on increasing the number of vehicles or speeding, which would have negative effects on environmental health. Having more vehicles on the roadway increases emissions and exacerbates traffic issues, while faster driving does not necessarily translate to environmental benefits. Finally, allowing more vehicles to be purchased would also lead to increased pollution and congestion, further harming the environment.