Doc: "I've got it! We simply roll it down a steep hill. No! We'll never find a smooth enough surface. Unless... Of course! Ice. We'll wait until winter, when the lake freezes over."
Marty: "Winter! Doc, what are you talikn' about? Monday, it's three days away!"
Doc: "All right, all right. Let's think this thing through logically. We know it won't run under it's own power. We know we can't pull it. But, if we can figure out a way to push it up to 88 miles an hour, huh? (train whistle blowing.) That's it!"