Someone has actually driven a real car around a Hot Wheels style loop-the-loop!

Fifth Gear is a British motoring television magazine series. The series puts cars to their limits, answers questions, and completes dangerous stunts. They decided to test the reality of the Hot Wheels loop-the-loop. The stunt could very easily be deadly, so they took many precautions. 

First, they built the world’s largest loop-the-loop with reinforced steel. Then, they sent their head stunt guy, Steve Trulia, to Cambridge University to speak with a Professor. They needed to know the amount of g force that Steve would experience to ensure that he wouldn’t black out. They also needed to know the optimal speed needed to pull the stunt off. 

Without that knowledge, he could fall from the tracks and die if he was going too slowly. They mathematically proved that Steve would need to go at least 36 miles per hour to safely make it around the loop-the-loop and that the amount of g force that he would experience would be 6G. To prepare himself for 6Gs, Steve took an airplane ride. They also reinforced the vehicle to withstand the force and strength needed for the stunt. Steve pulled it off beautifully and made it into the Guinness World Records for the stunt.