The 5.6km (3.5m) Bexhill to Hastings link road, in East Sussex, is due to open to motorists in the autumn.
East Sussex County Council said landscape planting and a greenway for cyclists, horse riders and pedestrians would not have to be finished.
Campaigners said the council was only interested in drivers.
Andrea Needham, of Combe Haven Defenders, said: "They're not concerned about carbon emissions increasing, they're not concerned about people in a very poor area that don't have cars, they're not concerned about the environment, they're not concerned about destroying the landscape of Combe Haven."
Karl Taylor, the council's assistant director of operations, said the changes to planning conditions were "a common sense measure" to ensure the link road was opened as soon as possible.
"We expect that the greenways for horse riders, cyclists and pedestrians will be completed by the time the road opens, but varying this condition gives us a little bit of leeway in case there is a slight delay of a few weeks," he said.
"The landscape planting, which was the subject of the other planning condition, can only be carried out during the planting season - which runs from November to April."
Mr Taylor added that the council remained totally committed to completing the greenway and the landscaping.
The multi-million-pound project was supposed to have been finished by May but has been plagued by delays.
Campaigners tried to halt construction, setting up camps and chaining themselves to vehicles, before archaeological investigations and bad weather caused further disruption.
A council has been accused of ignoring the interests of some road users and the environment after planning conditions for a new road were relaxed.