On 19 March 2013 a Boeing 727 freighter was cleared to take off on a runway occupied by two snow clearance vehicles. The subsequent cancellation of the take off clearance was not received but a successful high speed rejected take off was accomplished on sight of the vehicles before their position was reached. The Investigation attributed the occurrence to the controller's failure to 'notice' the runway blocked indicator on his display and to his non-standard use of R/T communications. The late sighting of the vehicles by the aircraft crew was due to the elevated runway mid section.