What do you get when you cross freestyle skiing with paragliding? Answer: the craziest, fastest, most extreme mountain sport adrenaline junkies can dream up.Speed riding is a high-speed, high-intensity and high-stakes (and, up until recently, mostly unregulated) mountain sport that allows for superfast speeds - we're talking up to 90 miles per hour - and access to terrain that would otherwise be off-limits to regular skiers or paragliders.