Borough High Street will be closed to southbound traffic between Southwark Street and Great Dover Street until July 2010 while Thames Water and Southern Gas Networks carry out major utility works.
"By getting Thames Water, Southern Gas Networks and TfL to work on-site together while this closure is in place, we have been able to halve the amount of time needed to carry out these works, saving motorists in the area from an additional seven months of disruption," says Alan Bristow, TfL's director of traffic operations.
Bus routes 21, 35, 40, 133, 343, N21, N35, N133 and N343 will be affected by the southbound closure.
The utility companies are employing a single contractor, Morrison Utilities Services, to work on the gas and water mains replacement works.
This means that if any problem occurs with the progress of work on one of the mains, the contractor can continue work on the other without any causing any delays.
Water main replacement work has recently been completed by Thames Water in Tooley Street.