Four members of pressure group Fathers-4-Justice have staged a protest on the Clifton Suspension Bridge in Bristol.
The protesters apologised for the inconvenience caused
The four men climbed on to a support at the Leigh Woods end of the bridge on Monday morning dressed as Batman, Robin, Superman and Spiderman.
At 0530 GMT, they unveiled a banner reading: "Fathers-4-Justice, Fighting for the right to see your kids."
Spokesman Jeff Skinner said the men apologised for any inconvenience to commuters who were denied access to the bridge.
"We and thousands of other fathers in this country are denied access to our children every day by this country's archaic family laws," he said.
The protesters said they would be staying for the "foreseeable future", despite the poor weather.
The bridge has been closed to traffic, although not pedestrians.
On Monday afternoon, one of the four men - dressed as Superman - came down from the bridge and left the protest.
Last week another Fathers-4-justice member carried out a similar protest on Plymouth's Tamar bridge which lasted seven days.
It is thought that as many as 15 members of Fathers-4-Justice met in Bristol on Monday from the west Country, coming from Cheltenham, Swindon, Lyme Regis, Worcester, Gloucester and Bristol.
One of the protesters, who gave his names as Jason, said: "We apologise or any inconvenience but we haven't seen our children for years.
"We've been fighting the law courts but getting absolutely nowhere."
A spokesman for Avon and Somerset Police said: "All efforts are being made to peacefully resolve the
situation as quickly as possible, though there is no indication of when the protest will end."
On Monday, Fathers-4-Justice issued a statement saying that today's protests were the start of a "full-scale national campaign of civil disruption".