Four members of pressure group Fathers-4-Justice have staged a protest on the Clifton Suspension Bridge in Bristol.
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." We apologise or any inconvenience but we haven't seen our children for years " "Jason"
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".
Fathers' group promises further protests
---------------------------------------------------------------------
A group campaigning for fathers' rights has warned that a series of protests on bridges is "just the start" of a nationwide campaign of civil disruption.
Several members of Fathers 4 Justice climbed bridges and gantries in Bristol, London and Newcastle on Monday, causing widespread traffic disruption.
Bristol's Clifton Suspension Bridge remained closed to traffic on Monday night, after three protesters dressed as cartoon super-heroes remained on it.One protester also remained on a gantry above the westbound carriageway of the A13 in east London, although the road stayed open.
Four other protesters were arrested in London after climbing gantries across the M4 and A40 and at the Blackwall Tunnel.
" All motorists have been denied access to the Suspension Bridge this morning as all our members are denied access to their children " Jeff SkinnerFathers 4 Justice
In the Bristol protest, four men dressed as Batman, Superman, Spiderman and Robin unveiled banners reading: "Fathers 4 Justice Fighting for your right to see your kids."
By Monday night, one of the protesters had left the bridge but the other three pledged to sit tight despite bad weather.
Spokesman Jeff Skinner said: "It's cold and it's wet but we are staying put and are not giving up. We will be here for the foreseeable future."
Mr Skinner said the men wanted to raise awareness of the "unfair" system of child access.
"All motorists have been denied access to the Suspension Bridge... as all our members are denied access to their children," he said.
An Avon and Somerset police spokesman 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."
In London, one man was arrested after protesting on a gantry above the A40 in west London, while another two were arrested after they protested on a gantry above the entrance to the Blackwall Tunnel in east London, which was shut northbound for a time as a result.
The fourth was arrested after protesting on a gantry above an elevated section of the M4.
The westbound carriageway of the A13 near Prince Regents Lane, where the fifth protester remains, was reopened after having been closed for some time during the day.
Fathers 4 Justice said it was planning to disrupt roads, railways and courts in a campaign of "widespread civil disobedience".
Spokesman Matt O'Connor said his members were ready to go to jail in their campaign of peaceful protest.
--------------------------------------------------------
Four members of the protest group Fathers 4 Justice have been convicted of public order offences and given conditional discharges.
Jason Hatch, 32, Patrick Lennon, 47, David Pyke, 48, all of Cheltenham and Mark Peacock, 31, of Bristol, appeared at North Somerset Magistrates' Court.
Bristol's Clifton Suspension Bridge was closed to traffic and pedestrians on 2 February during the protest.
The men were also ordered to pay costs of £250.
They were found guilty under Section Five of the Public Order Act of behaviour that caused harassment, alarm or distress.Passing sentence, District Judge Martin Brown, said: "It was unreasonable of you to remain on the bridge for so long.
"It follows that the irresponsible attitude expressed by the defendants infringed on the rights of others."
The four accepted that they had taken part in the demonstration, but denied offences under the Public Order Act.