"Standing on My Head"

Chesterton said he liked to stand on his head because the unusual perspective allowed him to see things as they are (or might be), not as he merely expected them to be.  I had an analogous experience while driving yesterday.  I saw part of a bridge over the Ohio River, but I did not immediately recognize it as part of a bridge.  What I saw was something like this

but what I thought I saw was more like this



This naturally got me thinking -- "Wouldn't it be cool to use the same trusses that support a bridge to also support a roller coaster?  I wonder if this has ever been done?"

Well, I found no evidence that it has been done, which is hardly a surprise.  It would be outrageously cool and could be the signature piece of the town that had it, but that is really the only thing it has going for it.

• Bridges are not infrequently hit by barges.  This could have disastrous consequences for a roller coaster on the bridge.
• If the coaster cars became stuck at the top, a rescue could really only be attempted from the surface of the bridge, and it would require closing the bridge.
• Drivers would be distracted, and perhaps dangerously startled, by the roller coaster.
• Objects thrown or accidentally dropped from the roller coaster would present a hazard to drivers.

In spite of all the good sense arguments against it, I'd still like to see someone build one.