The banner, which hung six metres above the motorway, said "Restore Passenger Rail" and came down early this afternoon.
Three people had been up on the gantry - a steel structure over the motorway which holds traffic signs - near Bolton St, since 8am.
The group's spokesperson James Cockle said the protest was to demand an expansion of the country's passenger rail network, making affordable rail connections available to all.
Another protester Tāmati Taptiklis said hanging six metres above a motorway while trucks rumbled below was not his idea of a good time. But this Monday morning, he felt compelled to be there.
Taptiklis is part of a group of rail advocates who have hung a banner from a gantry on Wellington's Urban Motorway near Bowen St, closing it to traffic.
Police issued a statement warning that motorists entering the city on State Highway 1 should expect delays. Diversions were in place for the southbound lanes.
Three people, including Taptiklis, were on the gantry - the grey steel structures which hold the traffic signs - from 8am, along with a large yellow banner that read "Restore Passenger Rail".
"We're certainly ready to be here for a quite a long time. Our goal is to kick off this campaign and get some attention," Taptiklis said.
"We've ticked all the safety boxes you can possibly tick while dangling off a motorway."
Cockle earlier said they did not take the decision to disrupt traffic lightly.
"We realise that this is an extreme response to the situation we're in, and we realise this may annoy people, and annoy drivers.
"We think their anger is justified, however, we think the response that we're taking is appropriate."
The group are asking the government to restore the passenger rail network around the country to what it was in the year 2000.
"That means making affordable passenger rail available to everybody right up and down the country. It will connect 3.5 million people, and we think that it's a great way to start to tackle the climate emergency," Cockle said.
"I expect they'll be here as long as they can, and probably until they're taken away by police."
