In 1956, Mercury had a Ghia-built concept car called the XM Turnpike Cruiser to show off. Since not everyone was going to get to see it at the car shows, they carried it on this glass-sided trailer so its flashy lines and and massive fins could be seen by all.
Debuting in Cleveland, the “idea car” as Mercury called it, featured see-through “butterfly roof” panels that would lift out of the way, headlights that stayed on for an extra 30 seconds once the ignition was cut and a set of wild body-exit exhaust pipes.
These features wouldn’t make it to the production Turnpike Cruiser which, despite an innovative retractable rear window, wouldn’t become the sales success Mercury was hoping for. The model was canned after two years.