Then dont make the train a giant surfboard, make them all individual surfboards such that they way you are standing looks somewhat proper.To all the comments about why not sideways — why? I wouldn’t want to ride a roller coaster turning my neck 90 degrees the entire time and potentially hurting myself because of sudden movements.
As Zachary pointed out somewhat if they would have themed this as something mythological or some story where we are all on some mystical magic surfboard, then I can see standing that way. But its not implied that way at all by the theming or the name.