Work on the controversial 2,500 home development near Faygate is causing traffic hold ups between Horsham and Crawley.
The Kilnwood Vale development will include a roundabout for access to and from the A264.
With construction work being carried out to the north of the A264, the eastbound carriageway is down to one lane.
The first phase of the plan will also see 291 homes built, together with a community green, known as the Gateway Village Green, a neighbourhood park, play and sports areas.
The 132-hectare (326 -acre) site was previously used for landfill.
Faygate is already earmarked for a large retirement complex at the site of the old sawmill.
This is likely to include a 50 bed care home and up to 148 retirement homes, together with new leisure facilities.
The website www.stopthehousebuilding.co.uk condemns the building projects as another intrusion into the strategic gap between Horsham and Crawley.
It raises the fear that Faygate may be ‘Crawlsham in the making’.