Caitlin McMahon was the latest arrested after allegedly obstructing trains near the Port of Newcastle in the NSW Hunter region on Tuesday.
The 26-year-old Lismore woman was allowed to leave court on Wednesday and barred from Newcastle unless attending court or meeting lawyers.
She is also not to enter a rail corridor, as part of her bail conditions, unless catching a train with a valid ticket.
Protests by the Blockade Australia group have been ongoing since June, with more than 30 arrests.
Rail, Tram and Bus Union NSW secretary Toby Warnes says the group's actions threaten safety.
"These actions aren't protests, they are negligent and dangerous.
"They put the lives of these individuals at risk and are reckless to the significant risk they pose our members," Mr Warnes said in a letter to Blockade Australia.
"While we understand that your organisation prides itself on pushing the boundaries, it is surely not in anyone's interests for deaths and lifelong injury to be the result, which is inevitably where this pattern of behaviour will end," Mr Warnes wrote.
Blockade Australia's Brad Homewood called for "genuine solidarity" after reading the letter addressed to him from the union on Wednesday.
"Most of the unions recognise that we're in a climate and ecological crisis and want to see the government take the appropriate action," Mr Homewood told AAP.
In the context of that crisis, the group would continue doing whatever necessary to draw attention, but safety was a priority, he said.
"We're not going to claim we know more about rail safety than the rail union itself," he said.
"But I think the fact that we've just done 16 days of sustained disruption and counting, and there hasn't been a single injury or a single death yet, speaks to how safely we've been carrying things out," Mr Homewood said.
