Symbolism, Imagery, Allegory
After a night of drunken carousing, Al Shockley and Jack run into a child's bicycle on the road. Jack is sure they've hit a child, but, apparently, they haven't. Jack and Al find no body and no mention of a child missing or dead in the papers. For Jack, the bike is a flashing sign: STOP DRINKING!!! And he does. The idea that he's killed a child literally scares him sober. It might be an especially scary image for him because of his history of hurting his own child, Danny, while drunk.