Semi Truck Jackknifes Off Bridge in Terrifying Highway Crash Allegheny County, Pennsylvania — February 8, 2024 Harrowing dashcam footage shows a semi truck losing control on a bridge before jackknifing and plunging off the side, sending the trailer crashing down below as traffic narrowly avoids catastrophe. The video captures the tractor-trailer beginning to fishtail on the elevated roadway, likely after hitting slick pavement. Within seconds, the trailer swings wide, slams into the guardrail, a