Rangers supporters using Glasgow's subway to travel to and from matches have been warned they could derail a train by bouncing up and down. Strathclyde Partnership for Transport (SPT) said fans doing "the bouncy" could cause an accident.
David Wallace, director of subway operations at SPT, said while the risk was small, fan safety was his priority.
Kenny Scott, Rangers' security manager, urged fans not to do "the bouncy" for their own safety. He said: "We encourage fans to enjoy their match day experience. "SPT has contacted us with regard to the dangers associated with supporters doing the 'bouncy, bouncy' on the subway and I would encourage all fans not to do this for their own safety. We don't want to dampen supporters' spirits ... but this is something that affects the safety of all those travelling on the subway and we urge our fans to take the advice of the SPT."
SPT said the issue was raised by a driver who found his train was handling differently with fans on board.
Mr Wallace said: "The major concern is that by adopting this 'bouncy, bouncy' there is the potential there for an accident. If you imagine a carriage with 100 fans on it all bouncing at the same time - if that reaches the same resonance frequency as the suspension there is a potential for the train to either rise or lurch to the side. It's a risk we don't want to take and we want to control it."
He added: "The vast majority of fans we transport do act responsibly and it is this small minority we're trying to get the message over to."
Mr Wallace ruled out closing the subway on match days.