This graphic shows an outline.

A list titled overcrowded city streets. There are two numbered lists below. 1, Cars are becoming too numerous on city streets. 2, The air is becoming polluted. 3, The noise level is rising. 1, More money from the city government should go to public transportation. 2, A subway system should be built. 3, People should be encouraged to carpool to work and school.

This outline is an example of

cause and effect.
order of events.
problem and solution.
order of importance.