A traffic light helps people and cars. It has three colors. The colors are red, yellow, and green. They are in a line. The red light is at the top. The green light is at the bottom. The yellow light is in the middle. Each color is a signal. Red means "stop." Cars must stop. Yellow means "wait." The light will change to red soon. Green means "go." Cars can go. People use traffic lights to cross the street safely. These lights are very important for safety on the road.