You may have noticed semi trucks with long pieces of metal hanging down toward the ground -- this is a side skirt, and here's what they're meant for.

You might have noticed empty flatbed trailers with a pronounced curve that's highest in the middle. This is why that arch is there and how it helps truckers.

Semi-trailers are a key pillar of freight transportation, carrying everything from groceries and furniture to heavy machinery across the country. These giant vehicles help keep the supply chain moving ...