As pointed out by theorists in the Blogger Beware comment section, A Shocker On Shock Street makes more sense when factoring in the protagonists' malfunctioning, which possibly explains the mounting insanity of the book. (Erin's "dad" says he knew something was wrong ever since the Erin robot asked about her mom. She was never programmed to ask about her mom.)
The park's tram has no seatbelts or normal safety precautions even before the terror starts. This is because Shock Street Park is still in it's testing phase, and the only visitors are two highly advanced androids. Mr. Wright probably built his "children" to be strong and durable, so human safety regulations wouldn't be a problem.
Why did the Giant Mantids attack the kids in the cave, if the park was supposed to be functioning perfectly? Because Mr. Wright designed them to be thinking, adaptive machines like Erin and Marty. The kids leaving the tram car before it moved again probably wasn't supposed to happen, since their AI was faulty, and the Mantises in turn reacted to two fellow machines going rogue.
