A further 40 miles (65km) of London’s road network are to be capped at 20mph (32km/h).
The lower limit is to be introduced on roads in Bromley, Greenwich, Kensington and Chelsea, Lambeth, Lewisham, Merton, Southwark and Wandsworth.
Signage work is expected to be completed by December.
Once the new zones are installed, Transport for London (TfL) will have delivered 87 miles (140km) of 20mph roads across the capital.
Will Norman, London’s walking and cycling commissioner, said the new limits would “help to make a large area of south London safer and more attractive for people to live and work”.
According to data collected in the central London congestion zone area from May 2020 to June 2022, the number of crashes fell by 25% compared with before the limits were introduced, TfL said.
The number of collisions resulting in death or serious injury decreased by 24%.
TfL said the figures should be seen in the context of a 10% London-wide reduction in collisions resulting in death or serious injury over the same period.
Mr Norman added: “Lowering speeds is one of the most important things we can do to reduce road danger and forms a key part of the mayor’s Vision Zero goal to eliminate death and serious injury from London’s transport network.”
The Met Police is understood to be on course to meet its goal, set out at the start of last year, of tackling one million speeding offences by 2024-25.
The force enforced about 620,000 speeding offences committed in 2022-23, an increase of 35% compared with the previous year.