A train traveling from Athens to Corinth split in half last week after its second carriage became detached from the engine while speeding along, without the driver realizing that he had left any passengers behind. Sources said yesterday that the carriage was stranded on the train lines in Kifissia, northern Athens, for 40 minutes before authorities detected the problem. It was not clear how many people were in the stranded carriage or how it became separated. Sources said that an electronic monitoring system helps a control center detect such problems but that the safety measure is out of order. Employees claim to have informed management of the problem on November 3. Sources added that a warning light informed the driver that the carriage was missing but he had not seen it.