CHICAGO (CBS) — A man hitched a ride on a semi-trailer truck in the most dangerous way possible, by clinging to the back of the trailer.

A driver following the truck at about 50 mph posted video of the incident on Twitter, showing the man waving, almost dancing as he dangles by one arm from the back of the trailer.

The truck appears to be heading north on the Dan Ryan Expressway, just south of the Byrne Interchange.

It’s unclear how long the man was on the back of the trailer, or if the driver was aware the man was back there.