Mega roller coasters of today reach heights of over 400 feet and speeds in excess of 100 miles per hour. Roller coasters towering taller than a certain height are terrifying for many individuals but it would be boring to simply make a list of the world's tallest coasters. As a result, most of the bone-chilling machines in this list do not use sheer height to terrify, but instead prey on our fears and emotions in other, more creative ways. One element alone may not make a ride terrifying but the sum of all of its parts does. What factors make a roller coaster terrifying? Height, speed, inversions, backwards segments, unique track elements, darkness, and unexpected surprises all contribute to making your head spin and your knees tremble. Where are the most terrifying roller coasters found? Who designs them? Which park builds the craziest rides? Find out by reading The 50 Most Terrifying Roller Coasters Ever Built! The second coaster book from Nick Weisenberger, author of Coasters 101: An Engineer's Guide to Roller Coaster Design which is the most in-depth look at how a roller coasters are designed, from concept through construction.