This book is filled with things that go. Vehicles are everywhere, from Jack's obsession with getting a car, to his Dad's J-3 wartime surplus airplane, to Mr. Spizz's giant kindergarten tricycle. So what's with all the wheels?
Getting a driver's license and finally sliding behind the wheel is a time-honored American rite of passage. It signals being able to go where you want, when you want and getting out there on your own. In a word: independence. That's true today, it was true back in 1962, and it's probably still going to be true when we're all driving around in hovercars.
So it's no wonder Jack can't wait for the day when he can buy his own car. He's already been driving the family tractor, and he's starting to drive cars around (at 12!), since Miss Volker needs his help getting around
When Jack gets his first real driving lesson (after only driving tractors), he's a bit scared. Miss Volker tells him in no uncertain terms to "try to be a man" (8.30). So, Miss Volker explicitly links cars and driving with being a grown up—and a grown-up man, at that. Jack uses the car in a show of manliness when he peels out in front of Mertie-Jo's, and we definitely get the sense that there's something about cars in particular that symbolized adult masculinity—especially in comparison to the other kinds of vehicles we see in Dead End in Norvelt.
As boys get bigger, so do their toys—and Jack's dad is a big kid with a really big toy. Mr. Gantos sees his airplane as a way to escape the dead-end town of Norvelt for someplace better: Florida. In his airplane, he can literally rise above what he dislikes about the town. And even though he's not getting what he thinks is his fair share of the American pie (which is a weird complaint for someone who thinks that everyone gets what they're able to earn), he can at least get a piece of the American sky.
Not that he knows what to do once he gets up there. On the airplane's maiden flight, Jack's dad dive-bombs Norvelt's empty, run-down houses, and even throws his shoes at them. Later, he vandalizes and terrorizes the movie theater and its patrons. Not cool, Jack's Dad. True to the extra-large and frankly bad-mannered kid that he is, the airplane ends is never more than a big toy, In fact, Jack's mom even calls it a "toy airplane" at one point. It's a perfect representation of Mr. Gantos's flighty personality. (Ouch. That pun hurt us worse than it did you.)
One last thing. Remember that Mrs. Vinyl thought Mr. Gantos's plane flying over her house was flown by invading Russians? She's wrong about the details, but her fear does make a kind of sense: the J-3 airplane, after all, is a World War II aircraft. Even though it's not a bomber or a warplane, it's still associated with war and destruction. Even though Jack's dad clearly doesn't intend to cause any real harm, it never really loses its more sinister and dangerous image.
Mr. Spizz is like a kid in many ways (think about the ridiculous argument he has with Miss Volker in the drug store), but he's bigger and way meaner than your average kid. Even the worst schoolyard bully doesn't usually resort to killing people to get his way. So, the "super kindergarten tricycle" (4.3) represents a super-sized selfishness and disregard for others. A normal-sized tricycle might represent childhood, but the size of the this one magnifies its meaning and focuses on all of the negative aspects of childhood: like being a selfish bully.
When Jack takes over the tricycle at the end of the book, though, its meaning changes. (That's the cool thing about symbols. They're not keys for decoding a story—they're way more subtle than that.) Now, the triangle becomes a symbol for Jack wanting to hold onto a part of childhood that is gradually slipping away from him. It also literally represents a "cycle"—cycles of life and death, and learning and growing that Jack has started to come to terms with by the end.
No wonder he thinks of the tricycle as "a pretty good ride" (28.49).