A few externalities do happen from cars on the road. Oil leaks are one. Aerosol pollution (black carbon type) from wearing down tires on the road. Roadkill i

A few externalities do happen from cars on the road. Oil leaks are one. Aerosol pollution (black carbon type) from wearing down tires on the road. Roadkill impact on wildlife. But they're dwarfed by non-environmental factors like road wear-and-tear, and accidents, which are covered by other taxes and insurance.