The Blue Flash is a roller coaster that John Ivers constructed in his rural Indiana backyard.
"I love to go to amusement parks and ride the the rides, but I can't stand waiting in line… To be honest with you, I'm not an educated engineer or mathematician or anything like that. It was more or less trial-and-error."
Here's a radio piece on Ivers and his coaster from WYNC's "The Next Big Thing." Link