A High Court challenge to the government's £27.4bn road investment scheme, which includes three schemes on the A47 in Norfolk, is to begin.
Transport Action Network has launched the legal challenge to the Road Investment Strategy (RIS2), claiming transport secretary Grant Shapps broke the law when approving it, by failing to consider the environmental effects.
A judge will hear the evidence on Tuesday and Wednesday and decide if the decision was lawful.
RIS2 includes three Norfolk A47 schemes - the dualling of the sections from Blofield to North Burlingham and from North Tuddenham to Easton, along with a revamp of the Thickthorn junction on the edge of Norwich.
Dr Andrew Boswell, a member of the Stop The Wensum Link campaign, said: "We are grateful to Transport Action Network for bringing this legal challenge on climate grounds against the government's £27bn road building programme including the Norfolk A47 schemes."
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