Very chilling! Could have ended up really bad. Props to the USAir 2298 Captain for not accepting the take off clearance from the tower. The tower controller was letting the situation take control of her actions, vice her controlling the situation. It sounded as if the female pilot on the United 757 had more situational awareness and control than her counterpart in the cockpit. They were obviously able to see all signs from the runway, but why couldn't they see the ones on taxiway November? Were they taxing too fast for the conditions? Did they utilize the runway diagram on the approach plates? The other aircaft taxing around the field didn't have problems seeing the signs, especially the USAir flight that had just arrived, and used the same taxiways that the UAL 757 was to use. If they really couldn't see the signs, couldn't they have asked for a progressive taxi or a "follow me" truck.