'Lots of safety checks' for rollercoasters
Alton Towers theme park has been closed while an investigation continues into a crash on their Smiler ride.
Four people were seriously hurt in the collision on Tuesday and were taken by helicopter to hospital.
Officials are trying to work out how it happened and how to keep people safe in the future.
Rollercoaster fan Justin Garvanovic told Ricky just how rare it is for accidents to happen, and the safety checks that are put in place.