Transportation: A green light for advanced train controls: Solid-state developments yield hands-off operation of second-generation systems

Discusses the second-generation train control systems which include automatic train supervision, using wayside central computers for integrating and stabilising the overall system. Other features include the use of wideband, bidirectional communication links which allow `moving´, rather than fixed, block control, thereby reducing headways and providing safe, closed-loop control. Several systems operating in late 1970s in the United States, Brazil, England, France, West Germany and Austria are outlined as an indication of future trends.