 Sissy Spacek (qv) asked Brian De Palma (qv) how he wanted her to  react when Carrie first realizes that she is bleeding in the showers  at the start, De Plama told her "Its like youve been hit by a  truck". Spacek talked to Jack Fisk (Art Director), who as a child  had been run over by a car when he was standing in the streets  looking at Christmas lights a neighbor had put up, and used his  description of the experience as a basis for the scene.