Smiler, 2015
On June 2, 2015, the Smiler roller coaster at Alton Towers in Staffordshire, United Kingdom, crashed against a test train. Two of the riders in the front row had to have their legs amputated and three other riders were badly injured. Six other riders were treated for non-life-threatening injuries. Investigators discovered that the roller coaster stopped when it detected the other train, but the ride operator thought it was a malfunction and overrode the safety protocols so the ride would continue. This is what sadly led to the horrible accident.