Escalators run at one speed: slow. But they could become high-speed transports if research at Mitsubishi pans out. Engineers there have invented a way to increase an escalator's speed by 50 percent on straightaways while maintaining a safe, slow pace at entry and exit points. The trick: Large-diameter pulleys at the escalator's edges force the rollers supporting the steps to take wide turns, slowing them down. Mitsubishi hopes to commercialize the variable-speed escalator within two to three years.