A breathless hush in the close tonight ...

(Except for a few 44-ton lorries)

A last-minute High Court challenge is being launched to prevent the construction of the Salisbury by-pass in Wiltshire which environmentalists say will destroy water meadows which are rich in several rare species of plant and a Site of Special Scientific Interest - and were immortalised by Constable's painting Salisbury Cathedral: From the Meadows.

The pounds 76m bypass on the A36 is expected to be given the go-ahead by ministers in the next few weeks, but Friends of the Earth has been granted leave to challenge the Department of Transport over its refusal to release a report on whether the road will increase traffic. Traffic generation has become a key factor in assessing plans since an advisory committee to the DoT reported last year that new roads do attract extra journeys. Since the report, all schemes have had to be reassessed but the DoT has refused to publish the new evidence in this case. It has been given until 21 October to file papers giving the reason for not releasing the report, which FoE says it must do under European legislation.

The decision to approve the by-pass is expected "within weeks" according to the DoT, a sign that it may be announced at next week's Tory party conference by Sir George Young, Secretary of State for Transport, who is known to be in favour of the scheme.

In the past couple of years half of the road programme has been scrapped because of the new report and budget cuts, and only a handful of new starts are expected this year. Campaigners against the Salisbury road argue that it is no longer part of a plan to link Southampton with Bristol. Simon Lyster, director general of the Wildlife Trusts, said: "This by- pass will not solve Salisbury's traffic problems but it will destroy irreplaceable wildlife habitat."