Technology: Up, Up and Around

Timid escalator riders who look twice before taking their first step will soon have something new to worry about. After years of trying, Mitsubishi Electric has developed a moving staircase that carries passengers not just up or down in a straight line but through a graceful, sweeping arc. The first two circular escalators will be installed next March in a shopping mall in Tsukuba, Japan. Cost: $325,000. A pair of conventional models, by contrast, costs $100,000.

The idea of a circular escalator seems simple enough, but the design problems were daunting. The challenge was to lift passengers up and around without tilting them, throwing them against a rail or squeezing them off the tread as it narrows while going around the turn. Complicating the problem were some basic laws of physics that say the two handrails must move at different speeds to match the motion of the twisting stairs. Still, the results look surprisingly conventional: a conglomeration of chains and sprockets and comblike metal plates ingeniously designed, machined and arrayed. The finished escalators will move 6,300 people an hour, provided they can first be persuaded to step on board.