At t = 0 a car is stopped at a traffic light.

At t = 0 a car is stopped at a traffic light. When the light turns green, the car starts to speed up, and gains speed at a constant rate until it reaches a speed of 20 {rm{ m/s}} 8 seconds after the light turns green. The car continues at a constant speed for 60 {rm m}. Then the driver sees a red light up ahead at the next intersection, and starts slowing down at a constant rate. The car stops at the red light, 180 {rm m} from where it was at t = 0.