IN A 44h changeover during February, Indian Railways put into operation its largest route-relay interlocking, to control the junction at Old Delhi. Designed by Siemens using 11000 Series K-50 relays, it controls 1122 routes on 28 running lines, with 238 signals and 188 sets of points. The station currently handles 222 trains and 634 light engine or shunting moves, and is used by 1·75 million passengers each day.