A Pedal Car is a transportation used for children.
Bart was driving, and Lisa was in the passenger seat and Maggie in the back. They got lost in the forest. Lisa tried to asked Jimbo, Dloph and Kearney for the right way, but she insulted Bart and it ended up with an argument. Eventually, Bart drove the car into a river and then used this to save Homer and Marge as they were falling off a tree over a gorge.
Lisa already owned a red pedal car when she was two years old. It got destroyed when she lost control going down a hill, crashed into a tree and exploded, with Bart saving her by a few inches.