From the Super Mario Wiki
A surfboard vehicle is an obstacle that appears in Mario Kart 8 and Mario Kart 8 Deluxe. The vehicles only appear in N64 Toad's Turnpike, where they drive along the road with the rest of the traffic, but are absent during battle mode. Similarly to cargo trucks, the player will spin out if they drive into them, having the same effect as driving over a Banana. Surfboard vehicles cannot be completely removed, but can be briefly launched into the air if driven into when using a Super Star or Bullet Bill. They may also honk their horns at the player if hit. The player can also drive up the surfboard on the back of the vehicle and use it as a Ramp, and are able to perform a Trick off the top of it, similar to a dash panel ramp truck. The vehicles themselves are purple pick up trucks, while the surfboards are yellow with a red flame pattern at the top and a Red Shell Strike Equipment sticker on them.