What will go-kart lovers do when the world goes hydrogen-car mad? According to one Dutch concern, they'll just trade in their two- or four-stroke engines for a fuel cell, hydrogen tank and electric motors. The company's built several incarnations of said karts and is promoting a new racing class, dubbed Formula Zero (for zero emissions), by way of a traveling race-circus of sorts. Got a county fair (albiet a European county) in need of some eco-racing action? They'll show up with a 600-meter racetrack, seating for 1,500, hospitality, pits, hydrogen generation and timing facilities for a full-on kart race. The only thing missing is the roar of internal-combustion engines and the smell of exhaust. But who needs those time-honored racing staples anyway. This may take some getting used to.