A motorcyclist is dead following a two-vehicle collision involving a tractor-trailer on Highway 401 in Oshawa, provincial police say.According to Ontario Provincial Police (OPP), the motorcycle crashed into the back of the tractor-trailer on the eastbound Highway 401 near Harmony Road just before 6 a.m. on Wednesday.No further details were released on the age of the motorcyclist.The OPP have closed the eastbound lanes of the highway from Harmony to Courtice Road.Police say the closure will remain in place for several hours.