Broken bridge pieces spark traffic chaos Cause of disruption ... loose steel plates on Sydney's Harbour Bridge. Text 0424 SMS SMH (+61 424 767 764), email us scoop@smh.com.au TENS of thousands of commuters faced an agonising trip home on Thursday after trains were stopped from travelling across the Harbour Bridge for more than three hours. The incident was the latest in a string of peak hour breakdowns on Sydney's public transport system even if, on this occasion, the problem was not caused by any failure of track, train or signalling equipment. Staff at RailCorp, the operator of Sydney's train system, discovered loose metal plates from the Harbour Bridge hanging over the line that crosses the bridge just after 6.20pm. RailCorp immediately suspended services between Wynyard and North Sydney due to fears the plates could dislodge and fall onto wires or tracks. But frustrations built across the city as commuters sought alternative means home, it was not until after 9.28pm that all plates were re-attached. Trains were not running again until 9.45 pm. The frustrations were compounded by an initial paucity of replacement bus services. RailCorp eventually put on 34 replacement buses, according to a spokeswoman. Some State Transit buses were redirected across the bridge. The buses were able to perform only a fraction of the job that would have normally been done by trains. About 40 train services would have headed north out of the city during the time the bridge's rail line was closed. The shutdown followed long delays on the Illawarra and Eastern Suburbs line on Thursday morning. And it came two weeks after peak hour services were suspended in the city because of a fire alarm at a signalling centre. The Transport Minister, Gladys Berejiklian, said: "I respect the decision of authorities to stop trains when several large metal plates from up on the Sydney Harbour Bridge above the rail line came loose - the safety of train customers has to be the priority."