Overturned Big Rig Leads To I-5 Freeway SigAlert An overturned big rig led to a SigAlert on the I-5 Freeway near Newhall Ranch Road in Valencia Friday afternoon. Around 3:30 p.m. Friday, emergency responders received reports of an overturned big rig on the northbound 5 Freeway near the exit for Newhall Ranch Road, according to Marvin Lim with the Los Angeles County Fire Department. “It was a non-injury (crash), so a lot of units have left the scene,” Lim said. A SigAlert has been activated due to the incident, with the northbound onramp to the 5 Freeway from the eastbound Highway 126 blocked for an unknown duration.