ODOT does their best to keep those roads plowed and sanded, but winter conditions are indeed treacherous. It's been many years since I've driven I-84 for a lot of reasons, among them the deer crossing danger. Have known several people who've collided with or swerved to avoid herds, with tragic results.
This accident is awful. The photo of the bus at the bottom of the slope made me cringe. The death toll keeps rising and it's been difficult for LifeFlight to reach the crash site.
Best wishes to all those involved. Such sadness to end the year!