T5 Gate 8 yesterday to Glasgow. Three lanes set up with relevant queues. Group 1 called to right hand scanner, Group 2 called to middle scanner and Groups 3-5 called to the left hand scanner at the same time. I'm not sure the gate staff had properly thought that through. The lead person in Group 1 had the red light on the scanner which caused a blockage. Those in Group 1 moved themselves on to the back of Group 2 which proved quicker.