Volunteers armed with speed guns recorded 40 drivers breaking the 20 mph speed limit in Bermondsey's Grange Road in just two hours.
The Metropolitan Police runs a Community Roadwatch scheme which trains volunteers to use hand-held speed guns.
Warning letters are sent to the registered keepers of vehicles found to be breaking the limit.
The SE1 website has obtained details of a recent Community Speed Watch operation in Grange Road under the Freedom of Information Act.
A two-hour Community Speed Watch operation was held in Grange Road on Friday 29 April.
"During this time, 40 speeding vehicles were logged," the Metropolitan Police told us.
"Of those 40, 32 letters were sent to registered keepers.
"We were unable to send letters in relation to the remaining 8 vehicles due to incomplete, or incorrect vehicle indexes being recorded."