Extinction Rebellion protesters shut down some access to the Blackwall Tunnel at rush hour in opposition to the Silvertown Tunnel project connecting Newham and Greenwich.
Theys set up on a slip road leading to the tunnel on Woolwich Road in Greenwich at around 7.30am on Friday, August 9.
After causing delays, they left at about 9am.
As well as showing opposition, the group wanted to inform people about the existence of the project.
Victoria Rance is the co-ordinator of the Stop Silvertown Tunnel Coalition and was at the event.
"The objective of the protest was to inform people about the Silvertown Tunnel. People who live right here didn't know about it."
Ms Rance said she saw a positive response from the motorists she spoke to.
Mariam Scharf, 64, is an ex-teacher of 30 years and is from Forest Gate. She is a member of Newham Extinction Rebellion.
"It's madness to go ahead with more car links. These projects have to be stopped," she said.
"Our children suffer from asthma. Children come into our playgrounds and breathe poison air."
The protest follows an open letter from Newham's mayor Rokhsana Fiaz urging Sadiq Khan to reconsider the Silvertown Tunnel.
At that time a spokesman for Mr Khan said: "Like the campaigners, the mayor has put tackling the climate emergency at the heart of his work. That's why when he became mayor, he worked with TfL to make significant changes to the Silvertown Tunnel scheme to better protect the environment."
He added the plans focus on cleaner transport, with buses using the tunnel expected to be zero emission and the crossing being located within the extended ultra low emission zone (ULEZ).
"The proposed user charges at both crossings ensure the scheme will not generate additional traffic or lead to an overall change in CO2 emissions and will deliver an overall improvement in air quality. There will also be monitoring of noise and air quality during and after construction."
A TfL spokesman said when the letter was sent: "We are committed to the project having a minimal impact on residents.
"Modelling demonstrates that overall traffic does not increase as a result of the scheme because the user charge can be set to manage demand for both tunnels."
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