Students at Arizona State’s mechanical engineering school have designed a mountain bike that “regenerates” the kinetic energy of braking. (Watch the video here!) In other words, it stores the energy of your momentum while you’re braking, and then allows you to accelerate again, without pedaling — rather like spinning that rubber band on your balsa model airplane or your Prius.

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You’re not going to see this contraption out on the singletrack though.

Your dream of coasting uphill is still going to require a some sort of internal combustion engine or a jet.