The diversions are the same as those in place for the second phase of works, which has been underway since 27 May 2008.
The diversions affect routes 177, 229, 401, 472, 601, 602 and N1.
Buses from Thamesmead follow the northern arm of Crossway to the Summerton Way roundabout, where they double back and then return along the northern arm of Crossway to Carlyle Road.
From the Carlyle Road/Bentham Road roundabout all routes will continue with their journey as usual.
Buses travelling in the other direction (towards Thamesmead) follow the same diversion in reverse.
Due to these diversions, buses are unable to serve the stops located on the southern arm of Crossway.
The works are being carried out by Tilfen Land, a local developer, and phase three will involve the bridge between Nickleby Close and Manor Close.
The works are expected to last approximately six weeks.
Once phase three is completed the bus routes will return to their original routing.
Passengers are advised to check posters on local bus stops for more information about the diversions.
Notes to editors: