A new national road protest group has joined forces with local residents in an attempt to halt work due to start on Monday on a £50m bypass.
Milton Keynes has been ear-marked for a huge housing development
Campaigners from Road Block aim to halt work on a five-mile route from Stoke Hammond in Bucks to Linslade in Beds.
People living nearby claim the road is being built for housing developments and expansion at Luton Airport.
More than 50 families with children and others started arriving at 0630 GMT but no contractors turned up to start work.
The planned road is the first piece of government-funded infrastructure designed to support John Prescott's expansion plans for the Milton Keynes and South Northants areas.
Campaigners say they are being forced to take direct action because at £40,000, the cost of challenging the project with a judicial review is too high.
Victoria Harvey, of Friends of the Earth, said: "John Prescott's growth means roads everywhere and Luton Airport growing from 7m to 30m passengers per annum.
"There is no guarantee that there will be any affordable housing for local people, nurses and teachers, let alone the money for hospitals and schools."
Supporters of the new protest group Road Block, launched at the protest on Monday, include "veterans" of the Newbury bypass campaign in Berkshire.
Stella Goddard, 36, who lives in Linslade, was at Monday's protest with her twin seven-year-old boys Francis and William.
She told BBC News: "This is beautiful countryside we do not want to see destroyed by the road."
The protest later thinned out as many of the families took their children to school and there was no sign of work starting.
A police spokesman said they believed work on the project would now start later in the week.
A Department of Transport spokeswoman said: "The government is committed to sustainable road building where necessary to improve safety and local conditions.
"The local authority planned the new bypass to reduce congestion at key periods of the day and relieve traffic levels in local villages."
The spokeswoman added that there were no plans for new housing although Linslade has been identified as an area for potential growth and any developments would undergo full consultation.