4. Driving an automobile generates many negative externalities. For example, driving creates pollution, since cars emit noxious chemicals when they're driven. Another example is traffic congestion; when one person drives, that increases traffic congestion for everyone else. Governments may try to limit the effect of these externalities in a variety of ways.

A. The two negative externalities listed above, air pollution and traffic congestion, are more and less severe at different times or in different places. What conditions make each of these more or less severe? (4 points)