Transport for London has revealed eight key roads to be turned into 20mph zones - and Commercial Street will be first.
The change will be made in April, at the same time as Tower Hamlets plans to bring in a wider speed capping system.
An 18 month period of close monitoring of the road will take place before a decision is made on whether to make it permanent.
Seven section to be included in the scheme after Commercial Street are:
- Upper Street and Holloway Road;
- Westminster Bridge, Stamford Street and Southwark;
- Brixton Town Centre;
- Clapham High Street;
- Earls Court Road and Redcliffe Gardens;
- Kings Cross Road and Farringdon Road;
- Camden Street.
TfL's managing director of surface transport Leon Daniels said the scheme was driven by an aim to reduce road casualties and increase cycling.
"Piloting 20mph speed limits form a key part of our continuing work to make central London safer, pleasant and more attractive for all," he said.
The plans have the support of Tower Hamlets mayor Lutfur Rahman, who said: “I am committed to making our streets and roads safer for all users to reduce accidents and injuries. The introduction of a 20mph limit is an effective starting point to achieve this aim.”
Tower Hamlets is due to make an announcement in the coming days on plans for a 20mph limit on a number of roads across the borough.
In a previous consultation it recommended all roads should have the cap apart from the A12 and the Limehouse Link/Aspen Way.