Train buff Alexander Fay jumped at his PhD advisor’s suggestion to design knowledge-based software to help human railway-traffic controllers in their struggle to keep trains running on time. When train breakdowns occur, some controllers tinker with track signals to reroute trains; others call for backup trains. Their decisions ripple through the rail system. Studies estimate $200 in lost economic opportunities for each minute a passenger train is late. Given Europe’s congested rail networks, the potential savings from better management is huge. After interviewing dozens of controllers, Fay used fuzzy-logic principles to integrate 150 when-this-occurs-do-that rules into his software. German Railways is now implementing his computer program, which standardizes the most efficient responses to service disruptions, in one of its regional control centers. Fay’s methods also apply to other systems. At Zürich, Switzerland, construction giant Asea Brown Boveri, he is developing software that captures the know-how of process and control engineers to reduce problems in designing and running pharmaceutical, chemical and energy plants.