Seems Vernal, Utah, is something of a centre for indeterminate saurians on highways, as this photo series by excellent dino-blog Love in the Time of Chasmosaurs shows.
Like most sauropods you see on the side of the road, the sculptor likely had no specific taxon in mind. Just a long neck, long tail, and some pillar legs, and you’ve got what springs to 90% of folks’ minds when they hear the word “dinosaur.”
But not all are generic dino shapes, as the fight between what’s apparently a ceratosaurus, stegosaurus and camarasaurus, shows. STEGO-STAB.