Estonian delivery robots headed for US must master crosswalks A knee-high, black-and-white buggy rolls down a snowy sidewalk in Estonia's capital Tallinn and, carefully avoiding pedestrians, stops obediently at the red traffic light of a large intersection. The six-wheeled robot on its way to deliver lunch to a client knows to cross only when the pedestrian light is green but armless, it cannot press the traffic light button. IMAGES AND SOUNDBITES