Protesters from a fathers' rights group have brought traffic to a near standstill on some of London's key roads.
The men from Fathers 4 Justice (F4J) climbed onto gantries on the A13, A2, M4, and A40.
Roads were closed for a short period while police assessed the scene but they have since reopened.
The protests are part of a campaign of events by F4J to raise awareness of the plight of divorced fathers.
A spokesman for the group said that the protests were the beginning of a full scale campaign of civil disruption.
A Scotland Yard spokeswoman confirmed on Monday that the Metropolitan Police's public order branch was policing a "number of demonstrations" across the city.
She said police were alerted to a man on a gantry above the eastbound section of the A40 in White City at 0730 GMT, but traffic was flowing.
In another demonstration a man had climbed on the gantry above the westbound carriageway of the A13 near Prince Regents Lane.
And another man had climbed a gantry near Canning Town flyover.
At about 0812 GMT police were told about two men on the Blackwall Tunnel northbound entrance, southern approach.
The entrance was later closed for safety reasons.
Scotland Yard said the two men were later arrested.
Police were also informed of another protest where a man had climbed on the gantry of the M4 elevated section eastbound into London.
There was no disruption to traffic in this protest.