You must be aware of the funnel sucking you out of a hole. In 1999 2 sought shelter under an interstate underpass. They got sucked out and dropped .25-.5 miles away.
an underpass is a dangerous place to be - will get sucked out - don’t go there, get in ground depression.
Underpasses are extremely dangerous in a tornado. The wind actually speeds up to get the same amount of air through a tighter area.