Years ago the Walt Disney World was looking for additional magical things to add to the roads for their upcoming Millennium Celebration. On a desolate piece of road on property speed warning indicators were tested (the kind you encounter on the side of the road or before a toll road) that played a song. That song was "Zip A Dee Do Dah", and for years it stayed there.
There were problems with it. First, was the fact in order for it to work, you would have to be driving a VERY specific speed, not faster, not slower, or it would seem like a random assortment of rumbles. And when someone would go the wrong speed, they'd think there was something wrong (veering of the road, toll soon, etc), and would try to break, get the car back on the road, etc, that it became dangerous.
Since it was dangerous, no one would drive the correct speed, and the fact they'd need to tear up the roads just to install it, Disney mothballed the idea.