The Kinetic Sculpture Races happen up and down the west coast. The vehicles must be human powered and they must carry everything they need for all four stages. The stages are an all out race on asphalt, a race on sand (in this case it was a hill climb on sand), a race on mud, and a race down the river. So you need to be able to go fast, climb your way out of sand, unstick yourself from mud, and float and propel yourself down water, and all be light enough that it's human powered. Not an easy engineering feat. Then add all the decorations and pagentry, and it's the iron-man competition for the engineering crowd.
The whole lot can be found here: