Traffic screeched to a halt on the 400 south of Barrie shortly after lunchtime Thursday. The OPP say a tractor trailer was southbound on the 400 around 1:00, when it somehow went through the guardrail and into northbound traffic south of Mapleview Drive. OPP Sgt. Kerry Schmidt reported six vehicles were involved in the crash that closed all but one southbound lane at one point. One person reportedly taken to hospital with minor injuries. The left lane in both directions was expected to be closed for several hours for guardrail repair. No word on charges laid.