Scarey older movie, family car breaks down on the side of an icy road, large truck skids around the bend & kills the mother & child...

The Changeling (1980)
Starring George C. Scott, Trish Van Devere (then Mrs. Scott), Melvyn Douglas
IMDb synopsis:
It was the perfect family vacation for composer John Russell and his family when a freak automobile accident claims the lives of his wife and daughter {{just as you describe}}. Consumed by grief, John, at the request of friends, rents an old turn of the century house. Mammoth in size, the house seems all the room that John needs to write music and reflect. He does not realize that he is not alone in the house. He shares it with the spirit of a murdered child who has homed in on John's despair and uses him to uncover decades of silence and deceit. With the help of Claire Norman, the one who aided John in procuring the house, they race to find the answers and soon learn that a devious and very powerful man guards them.

The Changeling (1980) - IMDb (http://www.imdb.com/title/tt0080516/?ref_=fn_al_tt_1)

Here's the movie trailer:
The Changeling (1980) Trailer - YouTube (http://www.youtube.com/watch?v=xTzgXVosQOU)