Salmonella, a belated welcome to the forum. Your's was a good find....a set of four 5000 series on the Blue line. Late Friday update.....My sources say, about the four-car 5000 series seen on the Blue line, it had nothing to do with revenue service, training, it had nothing to do with equipment being assigned to the Blue line. The train set was performing laser measurements which explains the equipment seen hanging out the front door. The 5000s have gone back to the Pink line. DH