A 12-hour protest has been staged against plans for an overground High Speed 2 rail link through west London.
Stop HS2 campaigners say 18 bridges will need to be replaced, including the Hanger Lane gyratory, to make way for the route.
Up to 10,000 vehicles an hour pass through Hanger Lane and Ealing Council wants the rail link to go underground.
An HS2 spokesman said contractors were studying both options and no final decisions had been made.
The demonstration, which was due to end at 19:30 BST, was held near the gyratory - one of the busiest intersections in London.
Protesters say three footbridges, 12 road bridges, one rail overbridge, one river underbridge and one canal underbridge will need to be rebuilt.
Ealing Council is not opposed to the rail link but wants trains to pass through a subterranean tunnel, a compromise those opposed to the rail link are willing to consider.
Kerry Brennan, from Stop HS2, said although the plan is "not a done deal" they want people to be aware.
She said: "Our protests engage people that will be affected by the HS2... to let them know that it isn't too late and it's time for them to have their say.
"HS2 are very good at trying to sell the benefits... but they have never come clean about the fact that they are going to have to rebuild huge parts of the Hanger Lane gyratory, if not all of it."
The HS2 project has not considered the cost of lost time for commuters, disruption to the Central Line on London Underground, and the loss to businesses as people might be put off from going to the area because of the traffic, she added.
'Catalyst for regeneration'
Peter Fry, from HS2 Ltd, said London would be a "big winner" in the scheme.
"HS2 will support the creation of some 20,000 jobs for Londoners, provide extra space on the existing lines for more commuter services, a completely revamped Euston station, and improved connectivity with our great northern cities," he said.
He claimed a new interchange station at Old Oak Common would provide "a catalyst for regeneration in west London".
"Our aim is to minimise the disruption to traffic by building temporary replacement bridges where we can, before replacing the current bridges," he added.
Mr Fry said bridges would be replaced in phases, and noise barriers would be introduced.
The final decision will be made by the secretary of state for transport.
In August, Councillor Bassam Mahfouz, Ealing Council's cabinet member for transport and environment, said: "A tunnel needs to be seriously considered and is the clear preference of residents from Northolt, Greenford, Perivale, Ealing and Acton to alleviate the serious issues they face under the current proposals."