Blofield to North Burlingham A47 upgrade approval challenged
A legal challenge has been lodged against plans to dual a section of road known as an accident blackspot.
A redeveloped 1.6-mile (2.6km) stretch of the A47 between Blofield and North Burlingham in Norfolk was approved by the government in June.
A climate activist has launched the challenge, claiming the government had "failed to lawfully assess the impact of carbon emissions".
The government said it could not comment on ongoing legal proceedings.
Andrew Boswell, a former Green county and city councillor, argued that Transport Secretary Grant Shapps had "failed to properly follow environmental regulations for assessing carbon emissions from this A47 scheme".
He also argued the £90m upgrade would "destroy unspoilt countryside while severing footpaths connecting Lingwood and Burlingham" - two villages east of Norwich.
National Highways, the government-owned company behind the plans, said it was working to lower emissions, adding the dualled road would be safer for the community.
If the courts accepted the case it could see judges review the government's approval, the Local Democracy Reporting Service said.
Police have said the section has been an accident blackspot where 33 people have died in crashes in the 10 years to 2021.
Work on the project was due to start in October, National Highways said.
Find BBC News: East of England on Facebook, Instagram and Twitter. If you have a story suggestion email [email protected]