Train drivers across the state sounded their train whistles on Thursday as part of protected industrial action about wages and conditions.
Rail, Tram and Bus Union secretary Alex Claassens said the initiative was the result of Sydney and NSW Trains management refusing to budge in negotiations on crucial issues such as safe cleaning of trains.
The use of whistles was mostly banned about five years ago due to noise complaints.
"Workers are fighting to prevent a drop in safety and hygiene standards on our trains, as both Sydney and NSW Trains are trying to cut cleaning jobs and force the dangerous New InterCity Fleet trains into service before its numerous safety issues are resolved," he said.
"After the government heaped rail workers with praise for putting themselves and their families in harm's way during COVID ... we've now entered enterprise agreement negotiations and any notion of goodwill has completely disappeared."
The union promised a "long list" of actions over coming months, but Mr Claassens said he was "hopeful" management would "come to the table".
