Why is there art on the Valley's freeways?

Valley 101 show

Summary: Drive down any of metro-Phoenix's highways and you're likely to see a highly curated display of graphics and flora. In Scottsdale, you can see large lizards and prickly pear pads gracing the walls of the Loop 101. Out west, dragonflies and checked flags come into view. And on the Red Mountain Loop 202, various indigenous animals and patterns are visible on both sides of the road.  But why do the freeways have art on them anyway? For that, Valley 101 turned to an urban historian and experts at the Arizona Department of Transportation. Turns out, there's a lot more to it than just making our highways pretty.