For over 150 years, railways have pushed engineering to its limits, in order to open up the world. Trains can now travel further, and climb higher, than ever before. But for train engineers, it's the need for speed that has inspired the greatest innovations of all. Trains can now reach previously inconceivable speeds, and record-breaking railways cross the globe. From mighty powered steam trains, super-sonic rocket sleds and trains that seemingly fly above their guideways; this episode investigates the incredible engineering breakthroughs that have made these trains go faster than ever thought possible.