A 40mph speed limit could be put in place by the Highways Agency along stretches of the A303 in Somerset.
It would be imposed on the approach and exits to the roundabouts at Sparkford, Cartgate, Hayes End and Southfields, where the limit is currently 70mph.
Mark Arberry from the Highways Agency said: "The plan has two objectives, to minimise confusion and improve safety through the roundabouts."
Agency studies showed there were 19 accidents between 2004-8 at Sparkford.
A public consultation period on the plans runs until 24 December.
If no-one objects to the proposals the new speed limit could be put in place by March 2011. The changes would cost the Highways Agency £155,000.