The legal battle against construction of the Aberdeen bypass will go to the UK Supreme Court in July.
Opponents previously said they were “disappointed” at the decision of Scottish judges to refuse an appeal.
Road Sense then said it would go to the Supreme Court in London, and dates of 9 and 10 July have now been set.
Transport Minister Keith Brown said steps had been taken to try and make the latest legal process as prompt as possible.
Campaigner William Walton has been fighting to block construction of the £400m project.
The 28-mile road was given the go-ahead by Scottish ministers in 2009.
Bypass supporters have called for moves to block progress to stop.
Many business leaders in the area support the scheme.