A rethink over a key roundabout in a major Northampton bypass plan that claims it will cut delays from 20 minutes down to 20 seconds has been labelled 'unbelievable' by campaigners.
Northamptonshire County Council has published a set of 'tweaks' to their controversial North West Relief Road scheme (NWRR) that it hopes will solve congestion worries.
The local authority was effectively sent back to the drawing board in July when traffic models predicted a new roundabout at Brampton Lane and Welford Road would suffer rush-hour jams of 20 minutes by 2031.
Now, a new traffic model by consultants WSP claims that adding an extra lane to two major arms of the proposed Brampton Lane roundabout will cut delays down to just 20 seconds in 2031 - compared to 20 minutes, as predicted in its last model.
But the fix has been baulked at by campaigners. Residents association WASPRA - a leading critic of the relief road - have called the new forecast "unbelievable", and have accused WSP of "rushing" their calculations.
The as-yet-uncosted plan is for a single carriageway between the A428 Harlestone Road and the A5199 Welford Road.
The bypass would effectively act as an access point to the 3,000-home Dallington Grange development between New Duston and Kingsthorpe.
Co-chair of WASPRA (Whitehills and Spring Park Residents Association) Sean Brady said: "There is no clear reason for this dramatic drop in predicted traffic.
"This is highly unrealistic and leads us to further believe that this application is being pushed through with sporadic calculations and unrealistic theoretical data.
"This 'magic roundabout' would be laughable if it wasn't part of such a grave matter."
WASPRA is calling for a conduct a full traffic assessment around the proposed bypass and to recalculate the expected delays.
It comes after WASPRA commissioned their own traffic survey of the Brampton Lane approach in July this year before presenting it to the council. WSP's new report admits that the association's data was "more in line" with real-world traffic flow than what had been used when they calculated the 20-minute delay.
The new model also takes into account an oversight in how much traffic on the relief road could come from the Dallington Grange development.
A consultation on the changes to the roundabout is open until October 26, and can be commented on using the county council's website.