You've probably noticed those giant flaps mounted on the backs of many semi-trailers you see on the highway. Here's what they're called, and what they're for.

UPDATE – Per NAPS, The ramp is now back open at I20 and US 25. Traffic is flowing normally. *** NORTH AUGUSTA, S.C. (WJBF) – An overturned tractor-trailer is blocking traffic in North… ...