Video narration
What has to sit beneath the road under your tires before it can carry traffic? First, the earth is shaped into a steady path. Low spots are filled, high spots cut back, and the ground is pressed firm so it won't shift under weight. Water has to be guided away; how that's done depends on the site. Then the road builds upward. A layer of strong material spreads the load across the ground. More support is added and compacted, making an even base for the surface. The exact materials and number of layers vary with the place and the road's use. Now the pavement goes on, smooth enough for travel. But pavement alone doesn't make a road hold up. Firm, shaped ground and compacted layers have to go beneath the finished surface. That's what lets the pavement do its job.