Campaigners are taking their legal action against the controversial £400m Aberdeen bypass to the Supreme Court.
Campaign group RoadSense are hoping to block plans for the planned Aberdeen Western Peripheral Route (AWPR), which has been 40 years in the planning.
A legal ruling from the Court of Session in February rejected the group's latest appeal and branded their arguments "misconceived".
On Thursday morning a RoadSense spokeswoman confirmed that preparations are under way to lodge an appeal with the Supreme Court, the UK's highest court.
She said: "RoadSense has been against the project since 2005. Our objections have not changed.
"We are strongly of the view that it is very important to use every method possible to try and stop the road.
"We have taken legal advice that there are grounds to proceed with an appeal.
"What we have been doing over the last few weeks is consulting with our supporters to see if they want us to carry on with the campaign, which they do."
The campaign group expects to submit appeal papers within the next week.
The spokeswoman said it could take up to seven months for the appeal to be heard.
She said: "It is not years. Hopefully the procedure would be over quite quickly.
"I know critics of our campaign say this is a delaying tactic. It is not. We want it resolved as soon as possible."
The 28-mile bypass was originally given the go-ahead by Scottish Ministers in 2009 after a four-month public inquiry.
RoadSense accused officials of failing to properly consult the public and also to make a proper assessment of the route.
They also claim the road will be detrimental to the environment, particularly on the River Dee, and the cost has been criticised.