A motorist is dead following a four vehicle pile up on the westbound Schuylkill Expressway near Gulph Mills. It happened shortly before noon on Friday. Investigators say a tractor trailer was unable to stop in time as traffic slowed in front of it. The big rig struck a car and the motorist inside was killed. Three other cars were also involved in the chain reaction accident. The drivers of those vehicles were treated for minor injuries at Paoli Hospital. The crash closed the Expressway for about four hours. It happened shortly after state transportation officials had opened a new off ramp from the westbound Schuylkill onto South Gulph and Henderson Roads. That exit gives motorists a new way to reach or avoid the King of Prussia Mall and should ease congestion at the Route 202 interchange.