Expanding on the topic of objects in motion covering Newton's laws of motion, acceleration and velocity, which are taught starting in third grade, students are introduced to new concepts of speed, density, level of service (LOS) (quality of roadways), delay and congestion. Every day we are affected by congestion—even if we do not step out of our homes. For example, the price we pay for goods increases due to increases in shipping costs caused by congestion delays. A congestion metric would help us to compare roadways and assess improvement methods. A common metric used to measure congestion is called level of service (LOS).