A SigAlert was issued after a car struck a flatbed truck on Interstate 8 in the El Cajon area.According to the California Highway Patrol, the incident happened shortly after 11 a.m. on westbound I-8 just west of North Johnson Avenue.Authorities said the truck carrying scaffolding made an unsafe lane change when it was struck from behind by a red Ford Mustang. A steel beam impaled the Mustang, lifting it off the ground and coming within inches of a person sitting in the passenger's seat.The Mustang's driver, Pejman Sagart, and his passenger had to be extricated from the vehicle. Sagart and his passenger suffered minor injuries in the collision, and the CHP said the crash caused the closure of the No. 4 and 5 lanes on westbound I-8.Sagart said, "I was coming up the ramp going maybe 45 to 50 miles per hour and the driver in front of me hit the brakes. I swerved to avoid him and this happened. Had I not moved quicker I could have probably got killed."The SigAlert was lifted at 12:11 p.m., the CHP said.The driver of the truck was arrested on suspicion of DUI. The truck is registered to a local plastering company.